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Maximal sagittal plane knee translation during stair walking was investigated in 5 healthy male subjects without any previous history of knee joint trauma during 2 types of ascents and descents (straight and side) using an electrogoniometer system (CA-4000, OS Inc., Hayward CA, USA). During the ascents, the tibia moved anteriorly in relation to femur, whereas during the descents it moved posteriorly. The maximum translations occurred within the range of 39 degrees to 51 degrees of knee flexion and were significantly larger during the ascents than during descents, but there was no difference between straight and side activities. There were significant interindividual differences in the maximum translations during the ascent or descent cycles but no differences between trials or the right or left limbs. The mean difference between repeated trials was 1.2 mm and the 95% confidence interval was +/- 0.6 mm.

We present the characteristics. of the scientific method and examine its effect on clinical facts. Because the scientific technique involves both reduction of facts (details) and generalization, it results in dangerous deformations of the clinical situation. Statistical methods used indiscriminately, as in many contemporary scientific papers, result in many false alarms and invalid therapies. Because of these limitations, the scientific method is not suitable for analysis of the true therapeutic situation, but can be used to gather biologic background facts necessary for the interpretation of observations made in the therapeutic situation. It is pointed out that clinical:experience is an ability to listen and observe that goes beyond science.

Equipment which measure femorotibial motions indirectly by using a patellar pad are reported to have errors caused by deformation of soft tissues and slippage of the device. For the purpose of validation, the tibial translation in relation to the femur per degree of knee extension was estimated from the slope coefficients of the flexion-displacement curve, obtained by both fluoroscopic and electrogoniometric tests, in the knee of the dominant limb in healthy subjects and in both knees of patients with unilateral anterior cruciate ligament (ACL) deficiency. In addition, the anterior and posterior static knee laxity limits and the tibial resting position were evaluated. Within all knee groups, the tibia moved posteriorly in relation to the femur during extension. The measured movement was similar both with the electrogoniometer and with fluoroscopy thereby indicating that sagittal plane knee translation measurements with the CA-4000 electrogoniometer are reliable and in good agreement with the X-ray measurements, even though the measurements were made separately. The ACL injured knees showed approximately 20% smaller posterior movement of tibia in relation to femur per degree change of knee extension than the non-injured or control knees (p < 0.05) and a more anterior resting position of the tibia relative to femur as compared to the contralateral healthy knee during knee laxity testing (p = 0.002).

A complete rupture of the anterior cruciate ligament (ACL) results in static and often in functional instability. After an ACL-injury, most patients have to decrease their activity level, while some can cope with their injury and manage to keep a high activity level. A better tmderstanding of the influence of muscle activation and external load on the non-injured and injured knee, but also of the adaptive motion strategies employed by the patients with an unstable knee, is of importance for the construction of rehabilitation programs.The general purpose of this thesis was to study certain knee motions during activities focused on rehabilitation, in individuals with anterior cmciate ligament injury and uninjured controls. The sagittal tibial translation and knee flexion angle were registered during motion with the CA-4000 computerized electrogoniometer and EMG was used for analysis of muscle activity. The injured knee had increased static laxity compared to the contralateral non-injured knee and the non-impaired group.The amount of tibial translation increased with increased quadriceps torque during nonweight bearing activities (isokinetic and isotonic contractions). In the non-injured knees, the restraining mechanism was engaged above 50% of isokinetic concentric quadriceps torque and during the eccentric contractions already at low quadriceps torques (

Three-month-old male rats were subjected 3 times weekly for 1 h to eccentric exercise of one triceps surae muscle (30 stimulations/min) under general anesthesia in order to induce Achilles tendon disorder corresponding to paratenonitis and tendinosis in man. Net muscle work during the sessions ranged between 0.67 and 4.37 mJ (mean 1.72, SD 0.77). After 9 and 13 sessions, respectively, 2 rats started to show gait alterations during the functional test which was performed 2–3 times weekly. These rats were killed after additional sessions which showed a worsening of the limp. The other trained rats and controls did not limp and were killed after 7–11 weeks. Histologic evaluation of the Achilles tendons from the exercised limb showed in the majority of the cases hypervascularization, increased number of nerve filaments and increased immunoreactivity for substance P and calcitonin gene-related peptide. The tendons from the nonstimulated limb looked normal. The distribution of collagen types I and II appeared normal in the tendon and its insertion to the calcaneus. Inflammation of the epi- and paratenon could be provoked in the rat, but tendon changes corresponding to chronic tendinosis did not develop within 11 weeks with the used training regime. The clinical relevance of this model for chronic tendon disease needs to be evaluated further.

With an electrogoniometer system, we made bilateral measurements of the maximal sagittal plane anterior-posterior knee translations in 15 healthy subjects (controls) and 14 patients with arthroscopically confirmed unilateral anterior cruciate ligament deficiency during two types of ascents and descents (straight and side). In both groups, during the ascent cycle the tibia moved anteriorly in relation to the femur, whereas during the descent cycle it moved posteriorly. There was wide individual variation in maximal translation in both the control and anterior cruciate ligament-deficient groups (range, 1 to 12 mm; mean, 7 mm). The maximal translations were similar in both groups (P > 0.05), but they occurred at a significantly smaller flexion angle in the injured knees (38 degrees +/- 8 degrees) than in the control and non-injured knees (44 degrees +/- 8 degrees) (P < 0.05). The translation during step ascent and descent did not differ between the injured and control knees. These findings indicate that patients with anterior cruciate ligament injuries are able to control abnormal anterior translation during normal activity.

Restoration of musculoskeletal function is a fundamental goal of orthopaedic treatment. Until now, clinical orthopaedic concepts of injury, repair, and restoration of function of musculoskeletal systems have been described and understood primarily in structural and biomechanical terms. This perception probably evolved because the structural characteristics are the most readily visualized factors, both in the clinical setting (for example, pathological laxity due to a ruptured ligament or a fracture) and through the preponderance of structural and pathoanatomical data offered by most current imaging modalities. Structural characteristics are also the factors most directly altered by operative intervention, such as stability following repair or reconstruction of a ligament or fixation of a fracture. It is a common belief that the restoration of measurable structural and biomechanical parameters to an injured joint, such as the knee, indicates the restoration of function to that system. We do not share this view. In the past few years, emerging clinical and basic-science findings have indicated a much greater degree of underlying biological complexity. Evidence suggests that the correction of identifiable structural abnormalities is often not sufficient to restore a joint to its full preinjury level of physiological function. For example, replacement of a ruptured anterior cruciate ligament with a graft does not necessarily prevent pain, swelling, or degenerative changes in the knee, even if the increased anterior-posterior laxity that had been present before the procedure is restored to normal. This observation indicates that factors other than anatomical and structural ones probably contribute to the restoration of joint function after injury. We believe that, although these other factors are less easily visualized, they play an important role in the ultimate functional status of an injured musculoskeletal system, such as the knee. The purpose of this Instructional Course Lecture is to discuss the concept of musculoskeletal function and to …

Vereinfachte Rekonstruktion der abgerissenen Kniebander mit einer sicheren Verankerung im Knochen. Risse des medialen, hinteren Schragbandes am tibialen Ansatz. Ausris des Seitenbandes am tibialen oder femoralen Ansatz. Traktustenodese. Wiederverankerung des medialen Retinaculum extensorum. Wiederverankerung des Musculus vastus medialis nach Patellaluxation. Keine. Nach Aufrauhung der knochernen Ansatzflache eines rupturierten Bandes werden mit einem Spezialbohrer mit Stoppfunktion zwei bis vier vertikale Bohrkanale angelegt. In das jeweilige Bohrloch wird ein metallener Anker, armiert mit einem nicht resorbierbaren Fadenpaar, eingebracht. Ein Federsystem im Anker verhindert sein Herausziehen. Das Band wird mit den Faden im Anker am Bandansatz fixiert. Seit acht Jahren wurden in uber 200 Eingriffen unter der Verwendung des beschriebenen Ankersystems keine Komplikationen beobachtet.

In this prospective study we investigated 70 patients with chronic anterior instability who underwent anterior cruciate ligament reconstruction with a Dacron pros thesis. Fifty-five (79%) patients could be followed up at a mean of 9 years. Within the follow-up time, 44% (29 of 66) of the prostheses were diagnosed as ruptured; the annual rupture frequency was 5%. Second recon structions were performed for 20 patients (29%), 5 patients had third reconstructions, and 9 patients wanted no further surgical treatment. Fifty-two patients (74% of the original group) underwent radiographic examination. Eighty-three percent (43) of these pa tients had radiographic changes in the operated knee, and 40% (21 of 52) had joint space reduction up to 50%. The rate of radiographically detected osteoarthi tis was increased 10 times compared with the normal knee. Patients with medial instability and patients older than 30 years at the initial operation had more severe osteoarthritic changes. Based on the functional results of the patients with a ligament in place after 9 years, only 14% (10) of the original group had acceptable stability and knee function.

A complete rupture of the anterior cruciate ligament (ACL) results in static and often in functional instability. After an ACL-injury, most patients have to decrease their activity level, while some can cope with their injury and manage to keep a high activity level. A better tmderstanding of the influence of muscle activation and external load on the non-injured and injured knee, but also of the adaptive motion strategies employed by the patients with an unstable knee, is of importance for the construction of rehabilitation programs.The general purpose of this thesis was to study certain knee motions during activities focused on rehabilitation, in individuals with anterior cmciate ligament injury and uninjured controls. The sagittal tibial translation and knee flexion angle were registered during motion with the CA-4000 computerized electrogoniometer and EMG was used for analysis of muscle activity. The injured knee had increased static laxity compared to the contralateral non-injured knee and the non-impaired group.The amount of tibial translation increased with increased quadriceps torque during nonweight bearing activities (isokinetic and isotonic contractions). In the non-injured knees, the restraining mechanism was engaged above 50% of isokinetic concentric quadriceps torque and during the eccentric contractions already at low quadriceps torques (

Knee flexion and sagittal tibial translation were measured during stair ascent and descent as well as during maximal isokinetic concentric muscle work with an electrogoniometer chain in ten volunteers without previous knee injury. The tests were repeated 16 times for each knee on different occasions by two examiners. The standard deviation for repeated measurements was ± 1.3 mm and the 95% confidence interval for the difference between repeated measurements was ± 0.9 mm. The test-retest correlations were above 0.80 for the whole group of subjects. There were no significant differences between the right and left knee, different sessions or examiners. There was a wide range in the amount of translation between different individuals from 2.7 to 10.2 mm. The translations during stair walking were 30-50% smaller than during isokinetic muscle work and the coefficient of variation was therefore higher. There was no difference in translations between stair ascent and stair descent but the amount of translation was larger for cycles ending with both feet carrying body weight than for single support cycles. It is suggested that higher contact forces in the knee diminishes the amount of sagittal translation. This finding indicates that closed kinetic chain exercises may be preferable to minimize translatory forces in the rehabilitation after reconstruction of the cruciate ligaments.

We reexamined 43 patients with stable knees at a mean of 13 years after arthroscopic meniscectomy. The patients had a maximum age of 22 years at the operation and no patient had had previous surgery on the involved knee. At the follow-up examination, no differences in range of motion, muscle strength or tibial A/P displacement were seen between the operated and the nonoperated knees and 36 patients had no problem with their knee in daily life. Radiographic changes were found in the operated knee in 20 patients and in the nonoperated knee in 5 patients. 8 patients had a reduction of the joint space on the involved side, but none had more severe changes. Cartilage fibrillation at the index arthroscopy did not increase the radiographic changes at follow-up, but radiographic changes were commoner after subtotal meniscectomy (7/8) than after partial meniscectomy (17/35). These findings are similar to previous studies of arthroscopic meniscectomy of medium duration and do not differ considerably from studies of open meniscectomy.

Tibial anteroposterior displacement after anterior cru ciate ligament reconstruction with a patellartendon graft was followed prospectively for 2 years in 24 patients with an arthrometer. The femoral ligament insertion lo cation, in a lateral projection, and the change in intra articular fixation distance, measured with an isometer, were documented intraoperatively. Two years after sur gery, the overall mean injured-noninjured difference in anteroposterior displacement was 2.0 ± 2.3 mm. All grafts were fixed during surgery at 20° of knee flexion. Patients for whom this angle coincided with the angle of minimum intraarticular fixation distance (Group I), and patients who had a femoral ligament insertion location >2 mm anterior to the center of the normal anterior cru ciate ligament attachment (Group A) showed larger tibial displacement than the other patients. An injured- noninjured difference in tibial anteroposterior displace ment ≥3 mm was classified as failure. Groups I and A failure rates were higher than for the other patients. No correlation was found between anteroposterior dis placement and magnitude of the change in intraarticular fixation distance. We conclude that anterior femoral lo cations lead to larger sagittal play after 2 years than central or posterior locations and that the magnitude of the fixation distance is less important than the pattern.

We compared two cementless femoral components, the 'isoelastic' Butel stem and the more rigid PCA design, in a randomised, prospective study of 56 patients with a mean follow-up of 4 years (2 to 5). Patients were matched in 28 pairs, and one of each pair was treated with each femoral component. The isoelastic stem gave fewer signs of stress shielding radiologically, but both the Harris hip score and the visual analogue pain scale showed significantly inferior results at the two-year and three-year follow-up. The overall failure rates for the femoral components were 43% for the Butel and 11% for the PCA. These results contrast with those of earlier experimental and clinical studies, in which isoelastic properties appeared to be advantageous. This review emphasises the importance of controlled studies before an altered or new design of prosthesis is released on to the market for general use.

The secretion rates of thyroglobulin were measured under basal conditions and after exogenous and endogenous thyrotropin stimulation in 23 patients during surgery. In 11 patients with normal thyroid glands the median secretion rate of thyroglobulin was 0.7 pmol/24 h. Higher secretion rates were observed in 8 patients with nontoxic nodular goiter (median 22 pmol/24 h; p0.001) and in 4 patients with thyroid malignancy (median 2.2 pmol/24h; p0.05). Within 10 min after administration of highly purified human thyrotropin into the thyroid artery an increase of the secretion rates was observed in the 9 patients studied with normal thyroid glands and 5 patients with nontoxic nodular goiter. TRH administration to 5 patients induced a slight but nonsignificant increase of the secretion rate of thyroglobulin after 20 min. These results show that thyroglobulin is secreted directly into the thyroid venous blood. They also confirm that thyrotropin is an important regulator of the thyroglobulin secretion.

Proteoglycan fragment concentrations in joint fluid of rabbit knees with various degrees of secondary arthrosis after meniscal resection, meniscal substitution, and anterior cruciate ligament transection, were related to the gross appearance of the articular cartilage. Knees with normal cartilage were distinguishable by the concentration of proteoglycan fragments in joint fluid from knees with arthrosis. We found a correlation (r 0.61) between increasing arthrosis and increasing concentrations of proteoglycan fragments.

Reconstruction of the anterior cruciate ligament (ACL) is a technically demanding operation. Precise placement and orientation of the substitute are essential for its survival and function. Appropriate instrumentation is important to achieve this goal. Complex instabilities involving peripheral ligaments as well as axial deformities need to be properly addressed as well, otherwise the success rate for the ACL reconstruction with be low. Ruptured menisci should be repaired whenever possible. The postoperative rehabilitation must consider the patient's specific activity goals and include rehabilitation of proprioceptive muscle control. There is a wide selection of possible substitutes for the ACL, but so far the poatellar tendon strip seems to be the standard with the longest follow-up time.

A meniscal prosthesis made of Dacron with polyure thane coating was tested as a substitute for the medial meniscus in a rabbit experimental model concentrating on biomechanical behavior of the knee joint and gross and histologic evaluation 3 months after surgery. The results were compared to sham-operated knees, knees with a peripheral incision of the medial meniscus, and knees with a total meniscectomy. Knees with prosthe sis implantation had the same stiffness as knees with sham-operation or meniscal incision, but knees with meniscectomy were stiffer (P < 0.05). Knees with pros thesis showed lower energy storage during relaxation than knees with sham-operation or meniscal incision (P < 0.05). Energy storage in the prosthesis group was similar to the meniscectomy group. Partial or total ingrowth of synovial tissue into the prosthesis was present in 93%, and 63% of the incised menisci had healed. Cartilage changes were present in 70% of the prosthesis group, in 25% of the knees with meniscal incision, and in all knees with meniscectomy. The sham- operated knees were free from cartilage degeneration. Knees with prosthesis had the same frequency of car tilage changes on the femur, but had less changes on the tibia compared to knees with meniscectomy. A high rate of osteophyte formation was observed after pros thesis implantation as well as following meniscectomy, but the osteophytes were larger in the prosthesis group (P < 0.01). The most frequent and severe effect on the synovium was found in the prosthesis group (92%), but no foreign body reaction or loose Dacron particles were found. The Dacron prosthesis had a cartilage-protecting effect, but the biomechanical behavior of the knee joint was similar to meniscectomy. Knees with peripheral meniscal incision were similar to sham-operated knees.

1996; 67 (6): 533-535. I agree with the general line of reasoning in the article, although I would like to comment on a few points. Review of the extensive literature on propriocep- tion of ligaments has raised several issues in which repeated studies report findings contradicting the original study on a particular subject. This is men- tioned in the editorial regarding the work of Barrack et al. (1989) and Barrett (1991) on proprioception tests after acl rupture, but I missed several compara- ble instances.

We report short-term data from 82 consecutive patients with arthroscopic meniscectomy 1995-1998 in stable knees and without severe cartilage changes. All patients were treated as outpatients, the operating time was, on average, 23 SD12 minutes and 3 of 4 patients were back at work within 1 week. Almost half of the patients still had some knee problems 3 months after surgery, but thereafter a substantial improvement was seen. We also report original data from a consecutive series of patients having arthroscopic meniscectomy 1980-81. In that series, the frequency of total meniscectomies was higher, the operating time longer, but the time to recovery was shorter than in 1995-98. In contrast to 1995-98, most of the patients in 1980-81 were followed by the doctor and had supervised rehabilitation. However, sick leave was similar in the two series. The total costs for an arthroscopic meniscectomy in 1998 was less than half the costs in 1980-81. We conclude that the improved technique for arthroscopic meniscectomy during the last 15-20 years and less supervised rehabilitation have reduced the costs, but not the recovery time.

We have followed for 13 years a consecutive series of 31 patients who had open repair of a torn meniscus. They were between 13 and 43 years of age at the time of operation and all had intact stabilising ligaments. Comparison was made with a matched group of normal subjects of similar age and level of activity. The total rate of failure after meniscal repair was 29%; three of the repaired menisci did not heal and six reruptured during the follow-up period. At follow-up 80% of the patients had normal knee function for daily activities. Radiological changes were found in seven. Two had reduction of the joint space (Ahlbäck grade 1), one with successful and one with failed repair. In the control group of uninjured subjects one knee showed Fairbank changes but none had changes according to Ahlbäck. The incidence of radiological changes did not differ between the group with meniscal repair and the control group but knee function was reduced after meniscal repair (p < 0.001). We conclude that the long-term results of meniscal repair in stable knees are good with nearly normal function and a low incidence of low-grade radiological changes.

Knee ligament injuries are common in sport. A rupture of the anterior cruciate ligament (ACL) is the most serious of these injuries because it may cause long term disability. In this literature review, the frequency of post-traumatic gonarthrosis is examined. There are few long term prospective studies but a number of retrospective studies with follow-up times between 5 and 20 years have been published. These studies show that radiographic gonarthrosis is significantly increased after all knee injuries compared with the uninjured joint of the same patient. Isolated meniscus rupture and subsequent repair, or partial or total ruptures of the ACL without major concomitant injuries, seem to increase the risk 10-fold (15 to 20% incidence of gonarthrosis) compared with an age-matched, uninjured population (1 to 2%). Meniscectomy in a joint with intact ligaments further doubles the risk of gonarthrosis (30 to 40%), and 50 to 70% of patients with complete ACL rupture and associated injuries have radiographic changes after 15 to 20 years. Thus, an ACL rupture combined with meniscus rupture or other knee ligament injuries results in gonarthrosis in most patients. Ten to 20 years after ACL injury, gonarthrosis often presents as a slight joint space reduction or, occasionally, joint space obliteration (Ahlback grades I to II), but is usually not associated with major clinical symptoms. According to the few longitudinal studies, the progress of gonarthrosis is slow, and in some cases the condition seems to remain stable. Time is an important determinant for the degree of gonarthrosis and problems demanding treatment may be encountered only at > 30 years after the initial accident.

Static anterior-posterior (AP) laxity is one of the commonly used criteria in selecting patients for cruciate ligament reconstructions, but in reality dynamic AP laxity plays a more important role. The aim of this in vivo study was to compare the sagittal translation of the knee during active and passive motion, signifying dynamic AP laxity, with static AP laxity in healthy subjects (controls) and patients with anterior cruciate ligament deficiency. The sagittal plane knee translations were recorded and compared in both knees of nine healthy subjects (Controls) and seven patients with confirmed unilateral ACL deficiency during dynamic and static situations with an electrogoniometer system. In all groups during the ascents the tibia moved anteriorly in relation to the femur, whereas during the descents it moved posteriorly. The static anterior-posterior translation was significantly smaller in the control knee than in both healthy and injured knees of the ACL deficient group (P < 0.05). The injured knee showed the same laxity (92%) as the uninjured knee during dynamic activities, but it was 46% of static laxity. Also in the injured knees, the dynamic active laxity was larger during descents than ascents (P < 0.05). The results indicate that there is also a change in mechanics of the noninjured knee following injury to the contralateral knee and that this population of patients with ACL deficiency had good control over their abnormal anterior-posterior laxity.

Sixty patients with stable knees and arthroscopic menisectomy were matched into two groups according to the presence of early degenerative changes at the operation. Patients with severe cartilage changes were excluded. The patients were between 20 and 40 years of age at the operation and no patient had previous surgery on the involved knee. The intraarticular findings were documented at surgery and the patients were re-examined 12 to 15 years after the meniscectomy. Pre-existing cartilage fibrillation at the meniscectomy did not seem to influence the long-term results. At the follow-up no difference was found between the groups at the physical examination, in subjective complaints, in knee function and activity or in radiographic findings. In the total group 62% had early signs of arthrosis (Fairbank changes) and 42% narrowing of the joint space (Ahlback grade 1-2) in the operated knee. No one had more severe changes. Radiographic signs of arthrosis were 4 times commoner in the operated knee compared to the non-operated knee after partial meniscectomy and 7 times commoner in the operated knee after subtotal meniscectomy. Arthrosis at the follow-up was seen three times more often in patients older than 30 years of age at surgery than in younger patients. The functional outcome was good and 70% were still active in sports compared to 90% before the operation.

(1996). Cartilage repair: A critical review. Acta Orthopaedica Scandinavica: Vol. 67, No. 5, pp. 523-529.

The rabbit knee is a common model for meniscus replacement, but data on the failure load of its meniscal attachments are not available. Therefore we determined the tensile failure load of the normal attachment of the rabbit meniscus. Both knee joints of five adolescent New Zealand white rabbits were dissected, leaving only the menisci intact on the tibia. Both menisci were sectioned at the midpoint along the circumference, and the anterior attachment of the lateral meniscus and the anterior and posterior attachments of the medial meniscus were tested on a MTS 858 machine. In the rabbit, the posterior attachment of the lateral meniscus inserts on the femur and thus was not tested. All failures occurred within the soft tissue of the attachment. The anterior attachments had significantly different failure loads (lateral, 158 +/- 28N; medial, 108 +/- 25N), and both were stronger than the posterior attachment of the medial meniscus (75 +/- 23N, p < 0.05). There were no differences between left and right knees. The relatively high failure loads in the meniscus attachments may be indicative of the normal tensile loads developed in these structures and the demands on the fixation of a meniscal substitute.

There exists a substantial group of patients with unsatisfactory results following anterior cruciate ligament (ACL) reconstructions. This may be attributable to graft failure. Revision surgery, for the correction of abnormal anterior translation of laxity, requires a careful analysis of the causes of failure to ensure the success of the salvage procedure. This review attempts to present an overview of some of the important studies in the literature pertaining to the intraoperative and postoperative factors that probably cause graft failure. It was done by initial identification of the articles from a Medline database followed by the use of cross references. It shows that failures can be minimised by adhering to the correct operative and post-operative techniques wherein proper attention to the factors, such as: adequate notchplasty, proper tunnel placements, proper tensioning, adequate fixation, optimal selection and harvest of the graft, and rehabilitation, are ensured.

In a prospective, randomized study of cementless total hip arthroplasties, radionuclide images as well as radiographs were obtained at 6, 12, and 36 months postoperatively. The femoral component was porous-coated, rigid in 28 patients and smooth, isoelastic in 28. The radionuclide uptake was quantified in the regions of interest and correlated to the non-operated side. Among prostheses considered to be stable 3 years after surgery, the activity had normalized in the calcar region. The uptake was also reduced below the tip of the prostheses, but the activity was still 50 percent increased compared to the non-operated side. The isoelastic prosthesis showed less reduction of activity below the tip than the rigid prosthesis. Proximally, the isoelastic prosthesis showed no reduction of activity, whereas the rigid prosthesis had normalized the uptake at the 3-year control. A high rate of non-stable fixation was observed for the flexible prosthesis at the radiographic assessment, which may have contributed to the increased radionuclide activity. Sequential scintimetry may be used as a complement to the radiographic evaluation of the femoral component of the hip prosthesis.

In 10 patients who had reconstruction of the anterior cruciate ligament, the load and length changes in an artificial ligament substitute were measured during passive knee motion. Using a special drill guide, the ligament was placed within +/- 2 mm of the normal anatomic center on the femur. With the femoral end fixed with a bicortical screw the ligament was preloaded to 40 N at the flexion angle with the shortest intraarticular ligament length, usually 45 degrees. The change in load was then registered from 90 degrees of flexion to full extension. In 2/10 cases loads of > 200 N were registered in full extension, but the mean load was 160 N. There was a higher loss of load during the first extension/flexion cycle than during the 4th cycle. The load change correlated to the length change, but the degree of length change could not predict the maximum load level. There was a large variation in load levels between different knees, even with similar ligament placements, but the least change in load and length was obtained by an anatomic placement. Isometer readings did not predict the load level in the ligament substitute, but could indicate the angle of flexion with minimum load. Therefore, the isometer can be used to control the placement of the attachment points for the substitute. After fixation, fiber settling and stretching the ligament, as well as adaptation of the tissues, will tend to reduce the load levels.

Implants of polyurethane-coated polyester (Dacron), polyurethane-coated PTFE (Teflon), or uncoated PTFE were used to substitute the medial rabbit meniscus, and were observed over a 3-month period. Joint mechanics were similar for sham-operation, meniscectomy, or substitution with a coated implant. Joints with an uncoated PTFE prosthesis tended to be less compliant and to show greater load dissipation during relaxation. Cartilage indentation showed softening with all alternatives compared to sham-operation. Ingrowth into the prosthesis periphery was best with the PTFE implants. Both types of coated prosthesis retained their original shape, in contrast to the uncoated prostheses. To the naked eye the cartilage appeared unaffected only after sham-operation or implantation of a coated PTFE prosthesis. Osteophyte formation was common with all alternatives except sham-operation. We conclude that replacement of the medial meniscus with coated prostheses, especially the PTFE, was better than meniscectomy or using the uncoated prosthesis. However, cartilage softening and osteophyte formation indicate that joint mechanics were not restored to normal. © 1993 John Wiley & Sons, Inc.

Polyurethane-coated and uncoated polytetrafluoroethylene (PTFE) (Teflon®) and polyester (Dacron®) felts were used for repair of full-thickness cartilage defects in the rabbit knee. At 3 months the indentation characteristics and the histological appearance of the repairs were compared with those of a sham-operation, natural repair, and periosteal grafting. Joint compressive load-displacement and indentation characteristics of the cartilage adjacent to the defect were normal for all alternatives. All the repair sites had a higher compliance than had normal cartilage-bone, but synthetic grafting had values closer to normal than periosteal grafting. The adjacent cartilage appeared macroscopically normal, except with periosteal grafting and coated PTFE implants where it showed surface irregularities in some cases. With periostea! and uncoated synthetic implants the defects were completely filled, but not in the natural repair sites. Most of the coated implants failed by separation within the implant. On histological examination, ingrowth of trabecular bone from the base of the defect into the synthetic material was seen in all the specimens. The neocartilage ‘score’ was equally low with all the repairs reaching only one-third of the maximum points. All the repairs were associated with synovitis. Further, some of the knees with the synthetic materials repair had debris particles in the synovium. We conclude that none of the biological resurfacing techniques described achieved normal articular cartilage characteristics at 3 months, although the compliance of the repair site was closer to normal with synthetic than with periosteal grafting.

Seventy patients with chronic anterior instability under went anterior cruciate ligament reconstruction with a Dacron prosthesis pretensioned to 60 N. Of these patients, 49% (34) had combined medial instability, 32% (22) had failed previous anterior cruciate ligament sur gery, and 37% (26) had previous meniscectomy. At reconstruction, 12 patients had their medial instability treated; 22 did not. Follow-up intervals were 3, 6, and 12 months and then each year to 5 years. The 5-year followup included 69 patients; the other 1 had the ligament removed because of a synovial fistula at 8 months. Results were 23% prosthesis ruptures, 3% poor, 17% fair, 16% good, and 39% excellent. The 2-year results showed the same distribution, but a lower rupture rate, which was affected by placement of the tibial tunnel within the anterior one-third of the tibia (9 times increase) and coexisting nonrepaired me dial instability (5 times increase). Those patients with perfect placement of the ligament who also had good medial stability and no previous ligament surgery had no rupture at 5 years. The stability that was gained at surgery was gradually lost (-11.2% per year). At 5 years, the uninjured knee also had lost 41% of the preoperative stability; the mean laxity difference was within ±2 mm. The mean improvement in subjective knee function (Lysholm score 74.5 to 91.9) was main tained during the followup. The mean preoperative ac tivity level improved significantly, but did not reach the preinjury level. These results show that the Dacron prosthesis will not give acceptable results in salvage cases where other instabilities are left untreated.

A Dacron meniscus prosthesis was substituted for the medial meniscus in an anterior cruciate ligament (ACL) resected rabbit knee. At three months, the joints were evaluated biomechanically, with gross and histologic inspection. In a paired comparison with the contralateral knee, differences between ACL resection with intact, incised, or resected medial menisci were evaluated. Knees with intact menisci and ligaments served as controls. Because of cartilage destruction, soft-tissue hypertrophy, and increased anterior laxity, joint stiffness was less than normal in all ACL-resected knees. Ingrowth and stable fixation, especially of the posterior horns of the prostheses and the incised menisci, were rare. Almost all normal menisci had ruptured in the same area. Anterior cruciate ligament resection led to severe osteoarthrosis in both compartments, regardless of initial meniscal treatment. Knees with prostheses had the same incidence and severity of osteoarthrosis as knees with meniscus resection. Anterior cruciate ligament resection alone induced excessive osteoarthrosis and synovitis and diminished the effects of different meniscal treatments three months earlier.

The effects of meniscal substitution with a Dacron® or Teflon® prosthesis on rabbit knee-joint cartilage were studied by indentation tests, gross and histological inspection, analysis of proteoglycan fragments in joint fluid and an evaluation of synovial changes. Cartilage mechanics and cartilage morphology were similarly abnormal after meniscectomy and meniscal substitution. The elevated concentrations of proteoglycan fragments in joint fluid and the more severe synovial changes in joints with a meniscal substitute, as compared to meniscectomy, probably resulted from irritation of the artificial implant, but also reflected the remaining effects from the necessary bone drilling. In this short-term experiment, the use of an artificial meniscal substitute could not prevent cartilage degeneration after meniscectomy.

With the objective to evaluate an "isometry" measurement in an anterior cruciate ligament (ACL) substitute, in vivo measurements were taken on 10 patients undergoing reconstruction due to chronic ACL deficiency. Change in intraarticular length of a 1.2-mm test ligament, measured with an isometer, was correlated to the tension created in the same test ligament after fixation, measured with a piezoelectric load cell. The knee was passively moved through the 0-100 degrees range with the patient under general anaesthesia. Good statistical and visual correlations between length change and tension curves were found in individual knees. A correlation between total length change and maximum tension, for all knees grouped, was also found. Individual knees showed large variation in ability of the tissue to absorb load, resulting in a wide range of N/mm ratios between length and tension. Three knees with an isolated ACL injury all showed the least length change, implying a better restoration of kinematics in the absence of associated injuries. In nine of 10 knees the length change pattern could be used to identify the location of the femoral drill channel, as determined on an intraoperative lateral projection of the knee. Intraoperative isometry measurement can be used to predict the tension pattern in the reconstructed knee, but not the magnitude of tension. It will be useful to the surgeon in avoiding an anterior femoral ligament insertion site, which might threaten the integrity of the graft by tension rise in flexion.

Manual tests and 2 external devices were used together with roentgen stereophotogrammetry (RSA) and an active weight-bearing radiographic method to measure the sagittal laxity in 11 knees with anterior-cruciate-ligament rupture. In 5 knees no ligament surgery had been performed (unstable knees) and in 6 knees a reconstruction had been performed one year before the examination (stable knees). There were positive correlations between all methods, including the manual tests when all knees, both stable and unstable, were analyzed together. However, the mean values of the total displacement differed between the methods, especially when comparing the weight-bearing radiographs with the three other methods. Some knees with substantial displacement during passive loading did not show any displacement when weight bearing; the measurements thus depended on both the ligamentous laxity and the patient's neuromuscular control of the joint. When the stable knees were analyzed separately, higher mean values were recorded with the external devices than with RSA using 180 N load. This could be explained by an error from soft tissue deformation which added to the skeletal displacement when the external devices were used.

One hundred thirty-five patients were reviewed six to 16 years after anterior cruciate ligament repair or reconstruction. At follow-up evaluation, 60% of the patients demonstrated significant residual laxity on objective testing. Thirty percent of the patients reduced activity levels because of instability. Degenerative arthritis was noted to be more frequent in those patients who had been treated with total open meniscectomy than in those treated with arthroscopic partial meniscectomy, and it was more severe than in patients with intact menisci. Continued participation in high-stress sporting activities generally led to a high rate of further injuries, reoperations, and progression of osteoarthrosis.

The strain distribution in the proximal tibia in seven human autopsy specimens was investigated with strain-gauge rosettes attached on the medial proximal aspect of the tibia. The strains measured were about the same on the proximal bone and on the bone in the metaphysis. The direction of the minimal principal strain (compression) was about 45 degrees counterclockwise (left knee). After insertion of a unicompartmental prosthesis medially, a non-constrained prosthesis with a loose meniscus-bearing and a constrained prosthesis, the tensile strain was about four times higher in the most anteromedial gauge. No significant differences were found between prostheses. Tests were also performed with the two prostheses inserted into three plastic models. The constrained prosthesis was more sensitive to outward rotation of tibia versus femur, which made the femoral component climb up the slope of the tibial component and caused a marked change in the strain distribution compared to loading in the neutral position. With the other prosthesis, a malpositioning of the tibial component medially caused the meniscus bearing to lie close to the medial rim of the tibial component. An external rotation of tibia then made the system constrained and dramatically changes the strain distribution.

From a total of 293 patients who had an acute, com plete anterior cruciate ligament rupture, we selected all patients (N = 55) who had an anterior cruciate ligament rupture without associated meniscal or ligamentous injuries, and all patients (N = 52) who had an anterior cruciate ligament rupture combined with a rupture, and subsequent primary repair, of the medial collateral lig ament. Initially, all patients were assigned to one of two groups: conservative treatment of the'anterior cruciate ligament or augmented anterior cruciate ligament repair with the iliotibial band. In the 52 patients who had an anterior cruciate ligament rupture combined with a me dial collateral ligament rupture, the associated injuries to the medial collateral ligament and sometimes the posterior oblique ligament, meniscus, and arcuate lig ament complex were treated in a similar fashion, with out regard to the treatment of the anterior cruciate ligament. Ninety-nine patients (93%) were reexamined 35 to 74 months after the injury, and knee function was evaluated with subjective and objective criteria, includ ing functional tests. Patients who had been treated with augmented anterior cruciate ligament repair had supe rior stability with better subjective results and returned to strenuous activities more frequently than patients who had undergone conservative treatment. In those patients who had augmented repair, the prognosis did not differ between those who had isolated lesions and those who had combined lesions. Conservative treat ment of the anterior cruciate ligament with repair of the medial collateral ligament and other associated injuries, when present, resulted in an almost equally unfavorable outcome for patients with combined and isolated an terior cruciate ligament lesions.

Ten patients with medial gonarthrosis treated by unicompartmental arthroplasty were matched with ten patients who had high tibial osteotomy; their courses of rehabilitation were evaluated. All patients regained motion without problems, with no difference between the groups. Muscle torque was measured by a Cybex II dynamometer. The results six months postoperatively were better in the patients treated by unicompartmental arthroplasty than they were 12 months postoperatively in the patients treated by high tibial osteotomy. In the prosthesis group there was an increase in the maximal gait velocity and the duration of single support. In the osteotomy group there was no significant change. This difference in the results of rehabilitation constitutes an argument for arthroplasty in aged patients.