MINIMAL INVASIVE PERCUTANEOUS HERBERT SCREW FIXATION IN ACUTE UNSTABLE SCAPHOID FRACTURE

The purpose of this study is to document the percutaneous Herbert screw fixation technique with free-hand method to stabilise acute unstable scaphoid fractures and evaluated the clinical results. Thirteen patients with less than 14 day-old fractures were fixed by percutaneous Herbert screw and reviewed retrospectively for a minimum of 24 months (average, 37 months). All were men with an average age of 22 years. According to Herbert's classification, all fractures were classified as of the acute unstable (B2). Fracture union was achieved in all cases at a mean of 9.2 weeks (eight to 12 weeks). Return to work or school ranged from one day to three weeks according to their occupation. This percutaneous fixation technique using Herbert screw is a reliable and effective alternative for acute scaphoid fractures, which enables the patient to use the hand earlier with high satisfaction and minimum complication.

Negative pressure wound therapy for soft tissue injuries around the foot and ankle

BACKGROUND

This study was performed to evaluate the results of negative pressure wound therapy (NPWT) in patients with open wounds in the foot and ankle region.

MATERIALS AND METHODS

Using a NPWT device, 16 patients were prospectively treated for soft tissue injuries around the foot and ankle. Mean patient age was 32.8 years (range, 3-67 years). All patients had suffered an acute trauma, due to a traffic accident, a fall, or a crush injury, and all had wounds with underlying tendon or bone exposure. Necrotic tissues were debrided before applying NPWT. Dressings were changed every 3 or 4 days and treatment was continued for 18.4 days on average (range, 11-29 days).

RESULTS

Exposed tendons and bone were successfully covered with healthy granulation tissue in all cases except one. The sizes of soft tissue defects reduced from 56.4 cm2 to 42.9 cm2 after NPWT (mean decrease of 24%). In 15 of the 16 cases, coverage with granulation tissue was achieved and followed by a skin graft. A free flap was needed to cover exposed bone and tendon in one case. No major complication occurred that was directly attributable to treatment. In terms of minor complications, two patients suffered scar contracture of grafted skin.

CONCLUSION

NPWT was found to facilitate the rapid formation of healthy granulation tissue on open wounds in the foot and ankle region, and thus, to shorten healing time and minimize secondary soft tissue defect coverage procedures.

Bone transport over an intramedullary nail for reconstruction of long bone defects in tibia

BACKGROUND

Although long bone defects may be treated by callus distraction, frequent complications arise from the long duration of external fixation. To reduce such complications, bone transport over an intramedullary nail (BTON) has been done for tibial bone defect.

METHODS

In 12 patients (mean age, 46.1 years) of chronic osteomyelitis or bone defect, segmental transport was done using external fixator over an intramedullary nail. Prior to the index procedure, all patients had had serial debridements and five required myocutaneous or free flaps for covering of soft tissue defects. Using Mekhail's criteria, functional results were evaluated.

RESULTS

The mean transported amount was 5.9 (range, 3.5-12) cm. The mean external fixation index was 26 days/cm, and healing index was 62.6 days/cm. The primary union of distraction and docking site was achieved in all, except for one failure in union at the docking site, which required another bone graft. Except for one patient with associated ankle injury, all had excellent or good functions. There was one recurrence of osteomyelitis and one procurvatum of the proximal tibia of 10 degrees .

CONCLUSION

BTON may be a successful method in tibial reconstruction and allows patients to return to daily life earlier with relatively few complications.

Early failure of hemispheric hydroxyapatite-coated acetabular cups

Total hip arthroplasties with hydroxyapatite coatings have shown encouraging results after early-term followup. We presumed hydroxyapatite-coating on a smooth hemispheric press-fit acetabular cup would enhance bone osseointegration and maintain stability of cup after midterm (minimum 5-year) followup. Sixty-three patients had 70 consecutive total hip arthroplasties. Five patients (eight hips) died from problems unrelated to surgery. The remaining patients (62 hips) were followed up for an average of 7 years (range, 6-9 years). The mean age of the patients was 49 years (range, 23-61 years). The average Harris hip score improved from 59 points (range, 32-82 points to 82 points (range, 37-100 points) at final followup. There were seven acetabular component revisions. Of the 55 unrevised cups, 47 hips (85%) were stable by bony ingrowth, five hips (9%) were fibrous stable, and three hips (5%) were unstable with cup migration. Osteolysis around the cup was observed in 18 hips (33%). The average polyethylene wear rate was 0.15 mm/year. Survival rates of the cups at 6 and 8 years were 94.3% and 60.5%, respectively. Total hip arthroplasties using an hydroxyapatite-coated smooth hemispheric acetabular cup showed an unexpected high failure rate in terms of fixation, occurrence of osteolysis, and revision after midterm followup.

LEVEL OF EVIDENCE

Therapeutic study, Level IV (case series). See the Guidelines for Authors for a complete description of levels of evidence.

An arthroscopic analysis of lateral meniscal variants and a comparison with MRI findings

We reviewed 164 consecutive cases (158 patients) of arthroscopic examinations for lateral meniscal variants during the last 10 years. We classified lateral meniscal variants into four types by arthroscopic appearance, into six tear patterns by modifying O'Connor's classification, and compared magnetic resonance images (MRI) with arthroscopic findings. Regarding the four types, 131 cases were complete, 25 cases were incomplete, 4 cases were Wrisberg, and 4 cases were ring-shaped meniscus. The six tear patterns were as follows: 33 simple horizontal, 21 combined horizontal, 37 longitudinal, 27 central, 14 complex, and 12 radial tear. Among the 31 knees with a central tear or ring-shaped meniscus, we reviewed 25 MR images. Fifteen (60%) MRI findings were interpreted to represent a bucket-handle (displaced) tear of the normal C-shaped meniscus; 7(28%) MRI findings, a discoid meniscal tear; and the remaining 3(12%) MRI findings, a simple meniscal tear. Moreover, all ring-shaped menisci were interpreted as a displaced lateral meniscal tear on the MRI findings. Twelve patients (13 knees, 7.9%) had osteochondritis dissecans: Nine patients (10 knees) of them had a central tear, two patients (2 knees) of them had a simple horizontal tear of the discoid meniscus, and one patient (1 knee) had a ring-shaped meniscus. Twenty three patients (92.6%) with a central tear of the discoid meniscus did not have any traumatic events. For the differential diagnosis of a central tear or a ring-shaped meniscus from a bucket-handle tear of the normal C-shaped meniscus, we should take a careful history, in particular any traumatic events, we should also consider the possibility of misinterpreting the MR images though these images can provide additional information about associated abnormalities and probe carefully in the arthroscopic operations.

Vascularized compared with nonvascularized fibular grafts for large osteonecrotic lesions of the femoral head

BACKGROUND

Many authors have reported good results with the use of vascularized fibular grafts to treat large osteonecrotic lesions of the femoral head. To our knowledge, there have been no prospective case-controlled studies comparing the effectiveness of vascularized fibular grafting with that of nonvascularized fibular grafting for the prevention of progression and collapse of the lesion.

METHODS

Nineteen patients (twenty-three hips) with a large osteonecrotic lesion of the femoral head (Stage IIC in ten hips, Stage IIIC in two, and Stage IVC in eleven, according to the classification system of Steinberg et al.) underwent vascularized fibular grafting. This group was retrospectively matched according to the etiology, stage, and size of the lesion to a group of nineteen patients (twenty-three hips) who underwent nonvascularized fibular grafting during the same time period. A prospective case-controlled study of the two groups, with a mean duration of follow-up of four years, was then performed.

RESULTS

The mean Harris hip score improved for 70% of the hips treated with a vascularized graft and 35% of the hips treated with a nonvascularized graft (p < 0.05). At the time of the final follow-up, nine of the ten hips with a Stage-IIC lesion treated with a vascularized fibular graft had not collapsed whereas seven of the thirteen hips with a larger lesion (Stage IIIC or IVC) had collapsed. Three hips (13%) were converted to a total hip replacement. The mean dome depression measured 2.8 mm. In the group treated with a nonvascularized graft, five of the ten Stage-IIC hips had not collapsed and eleven of the thirteen hips with a larger lesion had collapsed. Five (22%) of the hips were converted to a total hip replacement. The mean dome depression measured 4.3 mm. The rates of radiographic progression and collapse were significantly lower and the mean dome depression was significantly less in the group treated with a vascularized fibular graft (p < 0.05).

CONCLUSIONS

Vascularized fibular grafting was associated with better clinical results and was more effective than nonvascularized fibular grafting for the prevention of collapse of the femoral head in a matched population with a Steinberg Stage-IIC or larger osteonecrotic lesion. The results of vascularized grafting were best when the procedure was used to treat precollapse lesions (Steinberg Stage IIC).

Vascularized compared with nonvascularized fibular grafts for large osteonecrotic lesions of the femoral head

BACKGROUND

Many authors have reported good results with the use of vascularized fibular grafts to treat large osteonecrotic lesions of the femoral head. To our knowledge, there have been no prospective case-controlled studies comparing the effectiveness of vascularized fibular grafting with that of nonvascularized fibular grafting for the prevention of progression and collapse of the lesion.

METHODS

Nineteen patients (twenty-three hips) with a large osteonecrotic lesion of the femoral head (Stage IIC in ten hips, Stage IIIC in two, and Stage IVC in eleven, according to the classification system of Steinberg et al.) underwent vascularized fibular grafting. This group was retrospectively matched according to the etiology, stage, and size of the lesion to a group of nineteen patients (twenty-three hips) who underwent nonvascularized fibular grafting during the same time period. A prospective case-controlled study of the two groups, with a mean duration of follow-up of four years, was then performed.

RESULTS

The mean Harris hip score improved for 70% of the hips treated with a vascularized graft and 35% of the hips treated with a nonvascularized graft (p < 0.05). At the time of the final follow-up, nine of the ten hips with a Stage-IIC lesion treated with a vascularized fibular graft had not collapsed whereas seven of the thirteen hips with a larger lesion (Stage IIIC or IVC) had collapsed. Three hips (13%) were converted to a total hip replacement. The mean dome depression measured 2.8 mm. In the group treated with a nonvascularized graft, five of the ten Stage-IIC hips had not collapsed and eleven of the thirteen hips with a larger lesion had collapsed. Five (22%) of the hips were converted to a total hip replacement. The mean dome depression measured 4.3 mm. The rates of radiographic progression and collapse were significantly lower and the mean dome depression was significantly less in the group treated with a vascularized fibular graft (p < 0.05).

CONCLUSIONS

Vascularized fibular grafting was associated with better clinical results and was more effective than nonvascularized fibular grafting for the prevention of collapse of the femoral head in a matched population with a Steinberg Stage-IIC or larger osteonecrotic lesion. The results of vascularized grafting were best when the procedure was used to treat precollapse lesions (Steinberg Stage IIC).

Total hip arthroplasty with the use of nonmodular cementless acetabular component

Sixty-seven hips in 63 patients who underwent total hip arthroplasties with the use of the nonmodular cementless acetabular component and alumina-on-polyethylene bearing surface were available for complete clinical and radiographic review at a mean follow-up period of 7 (range 5-9) years. The mean age was 59 years (range 34-75) years. The mean preoperative Harris hip score of 50 points improved to 93 points at final follow-up. One (1.5%) hip required revision for a recurrent dislocation. No component was loose radiographically at final follow-up. The mean linear wear rate was 0.07 (range 0.01-0.23) mm/y. At a mean follow-up of 7 years, there was no aseptic loosening. Further follow-up, however, is necessary to determine the potential advantage of nonmodular acetabular component for the development of pelvic osteolysis.

Percutaneous Plate Stabilization of Proximal Tibial Fractures

BACKGROUND

Despite various treatment methods, proximal tibial fractures are common injuries associated with poor outcomes and high rates of complications. To improve this, a percutaneous plating technique was performed to treat proximal tibial fractures.

METHODS

Twenty-four proximal tibial fractures (17 proximal fractures [AO 41] and 7 proximal shaft fractures [AO 42]) were treated using percutaneous plating with either or both sides without bone graft. One was an open fracture.

RESULTS

All fractures healed. The average time for fracture healing was 16.5 weeks (range, 8-24 weeks). Complications included one case of shortening (1 cm) and two cases of malalignments; one valgus of 6 degrees and one varus of 5 degrees. There was one case of superficial infection that was healed after removal, but no patient showed deep infection. Results were evaluated by the modified Rasmussen scoring system. Most patients had excellent or good results; only one patient had fair results.

CONCLUSION

Minimally invasive percutaneous plating can provide favorable results in the treatment of proximal tibial fractures.

Functional Outcome After Operative Treatment of Eight Type III Coronoid Process Fractures

BACKGROUND

There have been few reports about surgical outcomes of coronoid process fractures. Eight cases of clinical results of type III coronoid process fractures were reviewed.

METHODS

Eight patients with coronoid type III fracture were retrospectively reviewed. All were men with an average age of 33 years. There were three isolated fractures, two elbow dislocations, two radial head and neck fractures, and one medial collateral ligament rupture. An open reduction and internal fixation through an anterior approach with cannulated screws was used. The patients were followed up for a mean of 31 months (range, 24-60 months).

RESULTS

Average active elbow joint motion at the most recent follow-up was 105 degrees. The average Mayo Elbow Performance Score was 76.9 (range, 50-95). Of the results, there was one excellent, four good, two fair, and one poor.

CONCLUSION

Early open reduction and stable internal fixation provided a reliable method for the treatment of type III coronoid process fractures. Any associated injuries to the elbow and fracture comminution were considered as important prognostic factors.

Femoral lengthening over an intramedullary nail using the external fixator: risk of infection and knee problems in 22 patients with a follow-up of 2 years or more

BACKGROUND

The time for femoral lengthening is shortened if external fixation is combined with intramedullary nailing. However, several complications have been reported with this procedure.

PATIENTS AND METHODS

We retrospectively reviewed the outcome of femoral lengthening performed over an intramedullary nail using external fixation in 22 patients. These patients were followed for a mean of 3.2 (2-5.2) years. The mean age was 22 (13-35) years at the time of the index procedure. The mean lengthening was 5 (2.7-8.1) cm and the external fixator was removed after median 20 (8-30) weeks. The mean external fixation index was 24 (11-35) days/cm and the mean consolidation index was 43 (26-55) days/cm of lengthening.

RESULTS

3 patients who had a past history of infection or open trauma developed osteomyelitis which required removal of the nail. There were 4 knee joint complications when the lengthening was over 20%, including posterior knee subluxation and patella subluxation. In 1 patient, the lengthened segment collapsed with breakage of locking screws.

INTERPRETATION

Although lengthening over a nail can reduce the duration of external fixation, caution is required to prevent major complications.

Minimally invasive percutaneous plating of distal femoral fractures using the dynamic condylar screw

BACKGROUND

In distal femoral fractures, conventional open reduction and internal fixation causes complications because of excessive soft-tissue stripping. To prevent this, minimally invasive percutaneous plating was performed in distal femoral fractures.

METHODS

Sixteen supracondylar or intercondylar femoral fractures were treated by minimally invasive percutaneous plating with the dynamic condylar screw without bone graft. Five (31%) were open fractures.

RESULTS

All fractures healed except one. The average time for fracture healing was 17 weeks (range, 14-22 weeks). Complications included one nonunion related to early full weight bearing. No patient showed malunion or deep infection. Results were evaluated by modified Neer rating, and all patients had excellent or good results. Intra-articular fractures showed less favorable range of motion and clinical scores than extra-articular fractures.

CONCLUSION

Minimally invasive percutaneous plating with the dynamic condylar screw can provide favorable results in the treatment of distal femoral fractures.

Uncemented Harris-Galante total hip arthroplasty in patients with osteonecrosis of the femoral head. A 10-16-year follow-up study

BACKGROUND

There have only been a few reports regarding the long-term results of uncemented THAs in patients with osteonecrosis.

PATIENTS AND METHODS

We evaluated the long-term results of 65 consecutive uncemented total hip arthroplasties (Harris-Galante type I prostheses) in 54 men (59 hips) and 5 women (6 hips) with osteonecrosis of the femoral head. The mean age was 53 (33-64) years. The mean duration of follow-up was 12.5 (10-16) years.

RESULTS

9 femoral stems and 3 acetabular metal shells were revised. 2 polyethylene liners were changed due to excessive wear. A girdlestone procedure was done in 2 patients (2 hips) due to delayed deep infection. The mean polyethylene wear was 0.14 mm per year. 3 non-revised hips had pelvic osteolysis and 18 had femoral osteolysis. The 15-year survival rates, using failure defined as the removal of any component for any reason, were 85 (95% CI; 79-91)% for the acetabular and 80 (74-86)% for the femoral component and 70 (63-77)% for any of the components.

INTERPRETATION

The first generation of the HGP design was frequently associated with pain, unstable fixation, and osteolysis. Excessive wear was frequent. The cup showed better durability than the stem.

Cementless Metasul metal-on-metal total hip arthroplasty in patients less than fifty years old

BACKGROUND

Durable results of total hip arthroplasty have been difficult to achieve in young patients. We reviewed the intermediate-term clinical and radiographic results in a series of active, higher-demand patients who were less than fifty years old when they underwent cementless total hip arthroplasty with the use of the Metasul metal-on-metal articulation.

METHODS

Seventy total hip arthroplasties were performed in sixty-two patients who were younger than fifty years of age (average age, thirty-seven years). Two patients (two hips) had had a resection arthroplasty because of deep infection less than five years postoperatively and were excluded. Sixty patients (sixty-eight hips) were available for complete clinical and radiographic analysis after a mean duration of follow-up of seven years.

RESULTS

The mean preoperative Harris hip score of 49 points improved to 95 points at the time of final follow-up; fifty-six patients (93%) had an excellent result. No component was seen to be loose radiographically at the time of final follow-up. Only one focal area of pelvic osteolysis in one patient and two small focal areas of femoral osteolysis in another patient were identified. The hip with focal pelvic osteolysis underwent revision surgery with a liner change and bone-grafting of the osteolytic lesion around a stable component.

CONCLUSIONS

At a mean of seven years after arthroplasties with a Metasul metal-on-metal articulation, there was a low rate of osteolysis and aseptic loosening in this group of young patients. However, additional follow-up is necessary to determine any possible long-term deleterious effects associated with this metal-on-metal articulation.

Treatment of femoral shaft fractures in young children: comparison between conservative treatment and retrograde flexible nailing

Outcomes of pediatric femoral fractures treated with traction followed by cast (conservative treatment) were compared with flexible nailing treatment. Fifty-one femoral fractures (24 conservative, 27 nail) from 46 patients were studied retrospectively. Four cases of angular deformities greater than 10 degree were observed from the conservative treatment and none from the nailing group. Conservative treatment showed a wider variance of leg length discrepancy (LLD) and four cases showed severe LLD greater than 10 mm. The nailing group had no discrepancy. Retrograde flexible nailing may result in more reliable outcomes than conservative treatment for femoral fractures.

Recurrence of synovial chondromatosis of the glenohumeral joint after arthroscopic treatment

A case of primary synovial chondromatosis of the shoulder in a 15-year-old girl is presented. Plain radiographs revealed findings characteristic of synovial chondromatosis. The patient was treated by arthroscopic loose body removal and arthroscopic partial synovectomy of the glenohumeral joint. Although immediate postoperative radiographs showed no calcification in the joint, repeated radiographs at 18 months after surgery revealed recurrence of calcification in the subacromial space. Arthroscopic removal of all loose bodies and partial synovectomy appears to be a good method of giving symptomatic relief and early return to work. However, late recurrence should be anticipated.

Completely displaced supracondylar humerus fractures in children: results of open reduction versus closed reduction

This retrospective study was performed to understand the clinical results after closed reduction and open reduction in 35 children (mean age 6.4 years) with completely displaced supracondylar fractures of the distal humerus between 1996 and 2000. Closed reduction (21 cases) was attempted, with open reduction (14 cases) indicated in irreducible cases with or without severe swelling. After an average follow-up of 22 months, according to Flynn's criteria, the results were excellent in 18, good in 12, fair in 2, and poor in 3. The satisfactory results rates were similar for closed and open reduction. The unsatisfactory results were related to the poor initial reduction and redisplacement after operation. The mean Baumann's angle was 8.7 degrees in the closed reduction group and 6.6 degrees in the open reduction group. None of the patients showed restricted elbow motion of more than 10 degrees, even in two cases of hypertrophic scar in the open reduction group. Selective open reduction for displaced supracondylar fractures of the distal humerus produced as good results as closed reduction.

Percutaneous plating for unstable tibial fractures

Twenty-four unstable tibial fractures were stabilized with a narrow limited contact-dynamic compression plate inserted using a percutaneous plating technique under fluoroscopic guidance. The major indication for this technique was a tibial fracture for which intramedullary nailing would be difficult. There were 16 proximal or distal metaphyseal fractures and 5 segmental fractures in adults and 3 mid-shaft fractures in adolescents who still had an open physis. Of the 24 fractures, 22 healed without a second procedure; the two failures included one that required an early bone graft for severe comminution and another with a superficial infection that healed after early removal of the plate. There were no other infections. There were three cases of screw breakage, but they did not require a further procedure. At the final follow-up, one patient had healed with 5 degrees varus alignment and another with 10 degrees external rotation. All the patients had good knee or ankle function. We are confident that the percutaneous plating technique to treat unstable tibial fractures for which intramedullary nailing would be difficult will prove to be an alternative stabilization method, as it avoids the risk of infection or soft tissue compromise.

Distal tibia metaphyseal fractures treated by percutaneous plate osteosynthesis

Twenty-one patients with fractures of the distal tibial metaphysis, some with minimal displacement in the ankle, were treated by percutaneous plate osteosynthesis with a narrow limited contact-dynamic compression plate. Using the classification by the Arbeitsgemeinschaft für Osteosynthesefragen and Orthopaedic Trauma Association, 17 fractures had no articular involvement, whereas four included intraarticular extension. At final followup (mean, 20 months), all the fractures healed without second procedures and the mean union time was 15.2 weeks. One patient had malalignment of the limb with 10 degrees internal rotation, but there were no angular deformities greater than 5 degrees or any shortening greater than 1 cm. All patients had excellent or satisfactory ankle function. There were no infections or any soft tissue compromise. Percutaneous plate osteosynthesis is a safe and worthwhile method of managing such fractures, which avoids some of the complications associated with conventional open plating methods.

High bifurcation of median nerve at the wrist causing common digital nerve injury in endoscopic carpal tunnel release

A 45-year-old right-handed woman was treated by endoscopic carpal tunnel release under local anaesthetic. When cutting the proximal half of the flexor retinaculum with the retrograde blade, she complained of an electric shock-like pain in her middle and ring fingers. Open exploration of the carpal tunnel was performed and a laceration of the middle/ring common digital nerve, which bifurcated at the unusually high level of the wrist crease, was found.

Retrograde flexible intramedullary nailing in children's femoral fractures

We treated 31 femoral shaft fractures in 28 children with a mean age of 6.7 (5-10) years with retrograde flexible intramedullary nailing. There were 16 isolated fractures, while 12 children had associated injuries. The average time for union was 10.5 weeks and there were no delayed unions. There was one broken nail requiring change of treatment, but no infection or refractures. At follow-up after a mean time lapse of 27 months there was no limb-length inequality exceeding 1 cm and no malunion. We feel that femoral fractures in patients aged 5-10 years can be safely treated with retrograde flexible intramedullary nailing with minimal risk of surgical complications.

Biomechanical properties after pre-twist of canine patellar tendon

We studied what effect a rotational pre-twist of the patellar tendon had on its mechanical properties. We used the central strip of canine patellar tendons. The length, width and thickness of each specimen were measured and the specimens were mounted in custom-made aluminum pots. Five groups of 10 specimens each were measured with neutral rotation, 90 degrees external rotation, 180 degrees external rotation, 270 degrees external rotation and 360 degrees external rotation. The ultimate stress, ultimate strain, average elastic modulus, and strain energy density were measured. There were no statistically significant differences among the five groups. Twisting the graft up to 360 degrees did not decrease the biomechanical properties of the graft.

Primary unreamed intramedullary nailing for open fractures of the tibia

Forty-six open tibial fractures (42 patients) were treated by primary unreamed intramedullary nailing, with debridement of open wounds and treatment of soft tissue. According to Gustilo-Anderson classification there were 18 grade I cases, 18 grade II cases and 10 grade III cases. The incidence of infection was low with two cases of superficial infection and one of deep infection. The mean time for union was 21.9 weeks and the rate of nonunion was 10.8%. There was no significant difference in the mean time to union, infection rate and rate of nonunion with different site and grade of fracture, but there was a longer union time and a higher rate of nonunion in complex and comminuted fractures. Unreamed intramedullary nailing, with appropriate soft tissue treatment, gives good results in the treatment of open tibial fractures including grade III.

Fracture separation of the distal humeral epiphysis in children younger than three years old

This study evaluated the change of carrying angle and the causes of cubitus varus after the fracture separation of the distal humeral epiphysis in young children. Twelve cases of fracture separation of distal humeral epiphysis were treated from January 1995 to July 1997. The age of all patients was younger than 3 years old. A metaphyseal fragment was seen in all cases (Salter-Harris type II), but the size of the metaphyseal fragment was either a very small flake or a large Thurston-Holland fragment. Posteromedial displacement was seen in all cases. There were three treatment groups: closed reduction with percutaneous pinning, closed reduction with cast, and cast without reduction. Follow-up period averaged 23.5 months (range, 12-40). Cubitus varus deformity was seen in seven cases, and six of them had a partial defect of the medial condyle that was avascular necrosis. The methods of treatment, age of injury, and the type of epiphyseal injury had no influence on the development of cubitus varus, but avascular necrosis of the medial condyle was related to the cubitus varus deformity (p<0.05). The results of this study suggest that fracture separation of distal humeral epiphysis in young children is likely to produce cubitus varus deformity with the development of avascular necrosis of the medial humeral condyle.

Three dimensional shape reconstruction and finite element analysis of femur before and after the cementless type of total hip replacement

Computerized tomography was used to reconstruct a shape, and stresses in three-dimensional objects were analysed. The human femur, which has a very irregular shape, was chosen as an object. CT image data of a cadaver femur were transferred to a computer, and an edge extraction program generated the cross-section of bone by specifying a range of CT values for each slice. Pixel data from the CT scan are converted into a vector of points (x, y, z) which can specify the boundaries of bone. Lateral surfaces are defined by stacking up the slices and making use of the vectorized data. Intermediate and oblique cross-sections can be obtained by an interpolation technique. The constructed model was used as input data for the finite element analysis. To understand the stress distributions before and after the cementless type of total hip replacement, a three-dimensional finite element stress analysis of the bone-implant system was carried out, assuming micromotions between the stem and the femur. The analysis was done for both frictionless and friction cases, modelling the contact point with a gap element having isotropic friction. The analysis shows that the stress is not concentrated on the femoral calcar when the friction coefficient is large.

In vitro study of contact area and pressure distribution in the human knee after partial and total meniscectomy

Many investigators have attempted to find the cause of the osteoarthritic changes after meniscectomy. Alteration of the mechanical factors resulting in stress concentration, is now thought to be one of the most important causes but few experimental studies have reported the differences in contact area and pressure distribution after partial or total meniscectomy. By using pressure sensitive film, we have calculated the contact area and the pattern of weight distribution in three different situations; intact meniscus, partial and total meniscectomy. The experimental materials were obtained from 5 above knee amputation specimens. The knee joint was fixed in full extension to an Instron machine using an aluminium box and mounting resin. Load was transmitted to the tibiofemoral joint containing the special film, within a physiological range. Analysis of the contact area for each situation (intact meniscus, partial and total meniscectomy) was made by reviewing the film. By measuring the contact area after meniscectomy, we showed that the meniscus performs a load transmitting function in the knee joint. The medial contact area of the tibiofemoral joint with an intact meniscus is always larger than the lateral compartment (1.36:1), but in partial and total meniscectomy the difference between them gradually decreased. There was a minor decrease in contact area after partial meniscectomy and a much greater decrease after total meniscectomy. The degree of stress concentration in the contact area was increased when part or all the meniscus was excised. There was little change of contact area in the opposite, intact side of the joint after partial meniscectomy, but marked change after total meniscectomy.

Photoelastic analysis of stress distribution on the tibiofemoral joint after meniscectomy

Three-dimensional photoelasticity models of the knee joints were made of epoxy to observe the change in the status of stresses according to the size of defect in the meniscus. Three kinds of meniscus models were made of rubber. Through axial application of a vertical compressive load of 8 kg, equivalent to the joint reaction of 3000 N in the human knee joint, the patterns of the isochromatic fringes were observed and stresses around the knee joint were analyzed according to the size of the defect in the medial meniscus. Stress was increased in magnitude according to the size of the defect of the meniscus, and was focalized after meniscectomy. In the partial meniscectomy model, the maximum stress concentration point of the removed side migrated to the margin of the same side of the joint. But, in the total meniscectomy model, stresses were markedly increased in magnitude on both sides of joints, and maximum stress concentration points were more centralized. This centralization effect would contribute to the degenerative process of the knee joint after meniscectomy.