Early metallosis-related failure after total knee replacement: a report of 15 cases.

Metallosis is a rare cause of failure after total knee replacement and has only previously been reported when there has been abnormal metal-on-metal contact. We describe 14 patients (15 knees) whose total knee replacement required revision for a new type of early failure caused by extensive metallosis. A modification of a cementless rotating platform implant, which had previously had excellent long-term survival, had been used in each case. The change was in the form of a new porous-beaded surface on the femoral component to induce cementless fixation, which had been used successfully in the fixation of acetabular and tibial components. This modification appeared to have resulted in metallosis due to abrasive two-body wear. The component has subsequently been recalled and is no longer in use. The presentation, investigation, and findings at revision are described and a possible aetiology and its implications are discussed.

Lateral unicompartmental knee replacement: fixed or mobile bearing?

Between May 2001 and May 2003, 233 consecutive Preservation unicompartmental knee replacements (UKR) were performed. Of these, 30 were lateral UKRs (13%) performed in 12 men and 16 women (2 bilateral cases) with a mean age of 67 years (range 36-93 years). A metal-backed mobile bearing tibial component was used in 13 knees and an all-polyethylene fixed bearing tibial component in 17 knees. The patients were reviewed prospectively at 1 and 2 years. The 2 year results show no difference in range of motion or function between the mobile and fixed bearing versions of the Preservation knee when used on the lateral side. There were three early revisions, all in the mobile bearing group.

Effects of cold and compression dressings on early postoperative outcomes for the arthroscopic anterior cruciate ligament reconstruction patient.

Efforts to minimize the morbidity of anterior cruciate ligament (ACL) reconstruction include the use of cryotherapy and/or compressive dressings in the immediate postoperative period. We undertook the present study to determine if the alleged benefits of the Cryo/Cuff, which combines these modalities, are more attributable to its compressive effect rather than cold application. Seventy-eight patients admitted for primary endoscopic ACL reconstruction using a bone-patella tendon-bone autograft were randomized to receive Cryo/Cuff compressive dressings postoperatively. Forty subjects (Group 1) had the cuff applied with continuous circulating ice water using the Autochill device, while 38 others (Group 2) received the cuff with room temperature water. Cases were performed as inpatients and all subjects were administered intravenous morphine postoperatively via a patient-controlled infusion pump for the first 24 postoperative hours. At baseline, the groups were well matched in age, sex, duration of symptoms, operative time, and associated meniscal surgery. No significant difference between groups was detected with respect to length of hospitalization, Hemovac knee drainage, oral and intravenous narcotic requirement, or subjective pain as measured by a visual analog scale. No apparent complications related to the use of the Cryo/Cuff dressings were noted. The clinical effect of the Cryo/Cuff in this study was not influenced by the use of continuous ice water vs. room temperature water. Further study should focus on variations in compression to evaluate the clinical impact of this device.

Biodegradable rods in adult osteochondritis dissecans of the knee.

Symptomatic osteochondritis dissecans of the knee in skeletally mature patients does not follow a predictable natural history and there has been a trend toward internal fixation of the unstable fragment(s) where possible. Biodegradable implants are enticing for intraarticular use: implant removal is unnecessary and its degradation potentially allows a gradual shift of loading stress to the fracture site. Nine patients with a mean age of 18.6 years (range, 14-23 years) deemed skeletally mature by plain film radiography underwent internal fixation of fragments by 2-mm self reinforced polylactic rods. Six procedures were completed arthroscopically and three required arthrotomy. All fragments were of the medial femoral condyle. The procedure was tolerated well although three patients had early postoperative serosanguinous effusions develop that did not recur after one aspiration. At a mean followup of 33 months (range, 24-54 months), eight fragments radiographically were united whereas one remained ununited at 26 months, accounting for the one poor result in this series. Seven patients had good to excellent results according to Hughston's criteria and were satisfied with the procedure. One of these seven patients had a spontaneous effusion develop at 5 months that did not recur after aspiration and intraarticular steroid injection. Severe, unremitting synovitis did not occur in any patient. Internal fixation of osteochondritis dissecans of the knee with biodegradable polylactic rods provided satisfactory control of symptoms in the short term and resulted in radiographically stable lesions in eight of nine patients. These rods may be suited best for fragmented lesions with intact articular cartilage as an adjunct to drilling.

Failure strengths of suture versus biodegradable arrow for meniscal repair: an in vitro study.

Advances in our understanding of meniscal function and consequences of menisectomy have spawned meniscal repair techniques that yield success rates approaching 90% in properly selected patients. Biodegradable implants have been fashioned for meniscal fixation to simplify the technique and minimize neurovascular complications. We performed the current study to determine the in vitro biomechanical behavior of the BIOFIX Meniscal Arrow, a polylactic acid tack developed for meniscal repair. Eight pairs of menisci were harvested from cadaveric knees kept frozen before testing. Peripheral vertical tears were created in the posterior horn of all menisci, and each was subsequently repaired using a vertical loop suture of 2-0 Ethibond and a Meniscal arrow. Ultimate load to failure of each method was determined on a Hounsfield H25KM Universal Testing machine. The mean failure load for the suture group was 58.3 N compared with the Arrow group mean of 29.6 N (P < .001). All sutures failed by rupture at the knot but did not pull through the meniscus. All but one of the arrows failed by pulling out of the meniscus. The Arrows also permitted gapping at the repair site at considerably lesser loads than the sutures subject to strain. The concept of a biodegradable tack is appealing. Vertical loop sutures should be the standard by which their biomechanical performance is judged. We suggest modifications to the Arrow design that could enhance the fixation strength of this implant.

Femoral bone plug recession in endoscopic anterior cruciate ligament reconstruction.

Graft tunnel mismatch is a constant challenge in endoscopic ACL reconstruction with bone-patella tendon-bone allograft. Strategies for addressing this situation on the tibial side which include staple or suture fixation may compromise the postoperative pullout strength of the graft. We describe our technique for recession of the femoral bone plug as a solution to this problem and present our preliminary experience in a series of 100 consecutive patients followed-up to 1 year. Interference screw fixation was consistently achieved in both tunnels and recession did not influence anterior-posterior displacement by KT arthrometry.

Direct measurement of hoop strains in the intact and torn human medial meniscus.

OBJECTIVE: To measure the circumferential or hoop strains generated in the medial meniscus during loading of the knee joint and to examine the effect of longitudinal and radial tears in the meniscus on these strain values. DESIGN: An in vitro investigation measuring the circumferential strains in the medial menisci of cadaveric human knees as they were loaded in a materials testing machine. BACKGROUND: The menisci transmit approximately 50% of the load through the knee, the rest being transmitted by direct contact of the articular cartilage. Damage to the menisci will alter the pattern of load transmission as will meniscectomy. This study examined the changes in the mechanics of the meniscus in situ as a result of simulated tears to assess the effect of its load carrying capacity and the implications of surgery to remove part or all of a damaged meniscus. METHODS: Nineteen human cadaveric knees were tested. Windows were made in the joint capsule and strain gauges inserted into the anterior, middle and posterior sections of the medial meniscus. The knees were then loaded to three times body weight at speeds of 50 and 500 mm/min, with the knee joint at 0 degrees and 30 degrees of flexion. The tests were repeated following the creation of a longitudinal or a radial tear in the meniscus. RESULTS: The intact menisci showed significantly less strain in the posterior section compared to the anterior and middle sections (P < 0.003, with strains of 1.54%, 2.86% and 2.65% respectively). With a longitudinal tear this pattern changed with strains decreasing anteriorly and increasing posteriorly. There were also significant differences at different angles of knee joint flexion not seen in the intact meniscus. 50% radial tears reduced the strains anteriorly whilst a complete radial tear completely defunctioned the meniscus. CONCLUSIONS: This study has shown that there are significantly different hoop strains produced in different sections of the medial meniscus under load and the patterns of strain distribution are disturbed by meniscal tears. RELEVANCE: These results provide important data for mathematical models which must include non-uniform behaviour. They also have implications for the surgical management of torn menisci. Undamaged portions should be preserved and the integrity of the circumferential fibres maintained to ensure the menisci retain a load bearing capability.

The use of cold therapy in the postoperative management of patients undergoing arthroscopic anterior cruciate ligament reconstruction.

In this prospective, randomized study we assessed the use of cold therapy after arthroscopic anterior cruciate ligament reconstruction. Seventy-one patients were randomly allocated, without the knowledge of the single surgeon, to one of three groups: Group I had an ice water-filled CryoCuff fitted in the operating theater after surgery, Group II had room temperature water in the CryoCuff, and Group III patients had no CryoCuff. Patients were well matched for age, sex, and associated surgery. An independent observer measured blood loss, analgesic use, range of motion, and visual analog pain scores postoperatively. There were no differences between any of the three groups regarding the variables measured. The use of cold therapy devices as an adjunct to the postoperative management of these patients must be questioned.

Radiographic changes in the knee after meniscal transplantation. An experimental study in a sheep model.

Meniscal transplantation has been suggested as an alternative to total meniscectomy, which is now known to lead to long-term osteoarthritic degeneration of the knee joint. To evaluate the success of meniscal transplantation, we divided 28 sheep knees into 4 groups: total meniscectomy, allograft, autograft, and control. After a mean postoperative time of 21.4 months, we radiographed the excised knee joints in a loaded state and graded the radiographs for osteoarthritic changes. The knees with meniscectomies, allografts, and autografts showed significantly more degenerative changes than the control knees. However, there were no statistically significant differences between these three groups. The results of this study suggest that meniscal allograft transplantation does not protect the knee against degenerative changes.

The popliteus as a retractor of the lateral meniscus of the knee.

Because of inconsistencies in the literature regarding popliteus and its relation to the lateral meniscus, it was decided to investigate the influence on the behavior of the lateral meniscus of contraction of the popliteus muscle via arthroscopy. A series of 50 knees from 44 patients who underwent elective arthroscopic surgery were examined. During arthroscopy, popliteus was stimulated to contract using surface electrodes. Any resultant meniscal retraction was observed and recorded. Thirty-one knees showed such retraction, and no retraction was observed in the remaining 19 knees. The clinical implications of this study are limited, but the results may support a number of proposed theories. It may be concluded that in a population exhibiting normal, intact lateral menisci, popliteus variably acts as a retractor of the lateral meniscus.

Failure strengths of different meniscal suturing techniques.

The aim of this study was to measure the failure strengths of three arthroscopic meniscal suturing methods. The techniques investigated were a single horizontal loop, a double vertical loop, and a single vertical loop. Eleven human, lateral menisci obtained at autopsy were cut with a scalpel to simulate peripheral longitudinal tears. The menisci were then repaired with one suture at a time, using each of the three methods in turn. The two parts of the meniscus were then pulled apart using a computer-controlled materials testing machine until failure occurred, either by the suture itself failing or by the suture pulling out because of tearing of the meniscus. The horizontal sutures had a mean failure strength of 29.3 N, whereas the double vertical loop failed at 63.2 N and the single vertical loop at 67.3 N. The horizontal loop sutures and the double vertical loop sutures all failed by pulling out of the meniscus. The single vertical loop sutures failed by rupture of the suture itself. This study showed the superior mechanical characteristics of the single vertical loop suturing system over the other techniques tested. Owing to the more consistent failure strength, decreased costs, and shorter surgical time over the double vertical loop system, the single vertical loop technique is recommended for arthroscopic meniscal repair.

The natural history of meniscal tears in anterior cruciate ligament insufficiency.

We reviewed the meniscal status of 176 consecutive patients undergoing anterior cruciate ligament reconstruction acutely (less than 6 weeks from injury), subchronically (6 weeks to 12 months from injury), and chronically (more than 12 months from injury). The commonest tear was the single longitudinal vertical split of the medial meniscus. There was an increasing incidence of meniscal tears as the injury became more chronic, with a significant (P < 0.001) increase in medial meniscal tears; the incidence of lateral meniscal tears remained relatively constant. Seventy-five (43%) of the patients had one or both menisci repaired. Acutely, repair was performed more frequently on the medial meniscus than the lateral (80% versus 24%, respectively). All repaired menisci had single longitudinal tears unstable to probing. The incidence of repair dropped to 46% in the medial meniscus and 14% in the lateral meniscus in the chronic stage. Nineteen (25%) of these 75 patients (26 menisci) underwent a check arthroscopy at a minimum of 6 months from repair. All 21 medial menisci and all 5 lateral meniscal tears had healed; however, 1 lateral meniscus had torn along the line of the sutures. At an average followup of 40 months, 92% of the repaired menisci were still in situ and 8% that had required resection were related to the recurrence of anterior cruciate ligament instability. This study highlights the increasing incidence of meniscal injury in chronic anterior cruciate ligament insufficiency with the meniscal tears becoming more complex and therefore less amenable to suture.(ABSTRACT TRUNCATED AT 250 WORDS)

Advances in arthroscopic surgery.

Removal of the whole meniscus from the knee has been shown to be associated with a high incidence of degenerative change. The degeneration is proportional to the amount of meniscus removed. After meniscal injury, retention of the meniscus in part (partial meniscectomy) or in whole (meniscal suture) is preferable. Replacement of a previously removed meniscus (meniscal transplantation) may be feasible in the future. Fifty patients had arthroscopic partial meniscectomies performed alternately by standard mechanical techniques or by electrosurgical techniques. The latter group was found to have less pain and swelling. Another 46 patients had meniscal sutures performed on one or more menisci. Twenty-one of these patients had a follow-up arthroscopy for recurrence of symptoms and only one meniscus had not healed. Another single patient had a meniscal transplant, and a follow-up arthroscopy six months after surgery revealed the meniscus to be largely intact.

Field testing: assessment of physical fitness of disabled adults.

The objectives of this investigation were (i) to develop simple field-test procedures for examining the cardio-respiratory and muscular strength fitness of lower-limb disabled individuals and (ii) to compare fitness levels across disabilities and physical activity levels. Forty-nine disabled adults (42 males and 7 females) were classified according to (i) functional and/or muscular deficit and, (ii) level of habitual physical activity. A forearm ergometer test was used to determine peak oxygen intake (VO2 peak). Sex-specific regression equations developed from the direct test were used in conjunction with a modified Astrand-Ryhming equation to predict VO2 peak from sub-maximal test results. Likewise, an equation was developed to predict isokinetic upper body strength (UBS) from cable tensiometry and hand grip force. The predictive power of the sub-maximal ergometer test was fair (r = 0.67), while the isometric strength measurements were relatively effective in predicting isokinetic total UBS (r = 0.82). Class 1 differed significantly from all other classes with respect to VO2 peak and UBS. The more active individuals also achieved significantly higher scores (p less than 0.05) for both variables. This study shows that an estimate of peak oxygen intake and UBS can be obtained from simple field tests and that active disabled individuals are more fit than their inactive counterparts.