Four-strand hamstring tendon autograft for ACL reconstruction in patients aged 50 years or older

INTRODUCTION

Reconstruction of the anterior cruciate ligament using a four-strand hamstring tendon autograft in symptomatic patients aged 50 years or older is an accepted treatment option.

HYPOTHESIS

Four-strand hamstring tendon autograft although not universally utilized in patients who are at least 50 years old is an efficient procedure to control knee instability.

MATERIAL AND METHODS

In this retrospective, we analyzed the clinical outcomes of 18 patients treated from September 1998 to September 2003. Criteria for inclusion were the following: age above 50 years at surgery, chronic anterior laxity associated or not with meniscal damage; one or more episodes of knee instability and no prior ligament surgery on the involved knee. A same operative technique (arthroscopic single-bundle four-strand hamstring reconstruction, blind femoral tunnel, through anteromedial portals), a same fixation type (absorbable interference screws in femur and tibia) and a same rehabilitation protocol were used for all these knees. The IKDC 93 scores were determined pre- and postoperatively combined with anteroposterior and lateral views, single leg stance, 30 degrees flexion stance, and passive Lachman test (Telos) postoperatively.

RESULTS

At mean 30 month-follow-up (range 12-59 months), there were no graft failure and no loss of extension for any of these knees. Three patients complained of hypoesthesia in the medial saphenous nerve territory and one patient experienced posterior knee pain. All patients graded their knee as normal or nearly normal, all were satisfied or very satisfied with their operation. None of the patients reported instability. The Lachman-Trillat test was noted "firm end point" in 14 knees and "delayed firm end point" in four. The pivot-shift test was negative in 16 knees and mild positive in two. The mean residual differential laxity was 3.1 mm (0 to +6 mm) for the passive Lachman test. At last follow-up, the overall IKDC score was 7A, 7B, 3C, and 1 D. Patients with preserved meniscus (nine patients) reported a lesser degree of pain and a better residual laxity control compared with patients who had undergone a meniscectomy.

CONCLUSION

Age over 50 years is not a contraindication to select a hamstring tendon autograft for ACL reconstruction. This surgery can restore knee stability but does not modify the pain pattern in patients, who had a medial meniscectomy prior to the ACL reconstruction.

Reverse shoulder arthroplasty combined with a modified latissimus dorsi and teres major tendon transfer for shoulder pseudoparalysis associated with dropping arm

Although a reverse shoulder arthroplasty (RSA) can restore active elevation in the cuff deficient shoulder, it cannot restore active external rotation when both the infraspinatus and teres minor muscles are absent or atrophied. We hypothesized that a latissimus dorsi and teres major (LD/TM) transfer with a concomitant RSA would restore shoulder function and activities of daily living (ADLs). We prospectively followed 11 consecutive patients (mean age, 70 years) with a combined loss of active elevation and external rotation (shoulder pseudoparalysis and dropping arm) who underwent this procedure. All had severe cuff tear arthropathy (Hamada Stage 3, 4, or 5) and severe atrophy or fatty infiltration of infraspinatus and teres minor on preoperative MRI or CT-scan. The combined procedure was performed through a single deltopectoral approach in the same session. Postoperatively, mean active elevation increased from 70 degrees to 148 degrees (+78 degrees ) and external rotation from -18 degrees to 18 degrees (+36 degrees ). The Constant score, subjective assessment and ADLs improved. The combination of a RSA and LD/TM transfer restored both active elevation and external rotation in this selected subgroup of patients with a cuff deficient shoulder and absent or atrophied infraspinatus and teres minor.

Modified latissimus dorsi and teres major transfer through a single delto-pectoral approach for external rotation deficit of the shoulder: as an isolated procedure or with a reverse arthroplasty

Definitive loss of active external rotation of the shoulder impacts an individual's ability to perform ADL's, creating severe disability. To restore active external rotation, we modified the L'Episcopo procedure by transferring both the latissimus dorsi and teres major (LD/TM) through a single delto-pectoral approach. The two tendons were rerouted and reattached laterally on the humerus to the stump of the pectoralis major which was partially transected to the posterior epiphysis. Fifteen consecutive patients who underwent this procedure; (mean age 63.2 years), have been followed for at least one year (range 14-63). The transfer was indicated alone in 7 patients with an isolated loss of active external rotation (ILER) related to an irreparable postero-superior cuff tear. It was associated with a reverse shoulder prosthesis in 8 patients with combined loss of active elevation and external rotation (CLEER): 6 cases of rotator cuff tear arthropathy and 2 of tumor reconstruction. For the series as a whole, the mean increase in active elevation was 34.7 degrees . The gain in active external rotation was +27 degrees for ILER patients and +28 degrees for CLEER patients. Constant score improved to 65.6 (range, 51-79). Subjective shoulder value (SSV) was significantly improved from 34% to 72% (P < .0009). All but one patient was satisfied or very satisfied with the result. The major contributor to their satisfaction was the ability to control the spatial positioning of the arm, eliminating the tendency of the forearm to swing in toward the trunk. One patient had a return of a lag sign after a fall. The modified tendon transfer, performed in the beach chair position through a delto-pectoral approach, is less invasive than the classic two-incisions procedure and provides good functional results in patients with absent or atrophic infraspinatus and teres minor. When the modified LD/TM transfer is associated with a reverse shoulder arthroplasty, it allows to restore both active elevation and external rotation.

Human adipose tissue-derived multipotent stem cells differentiate in vitro and in vivo into osteocyte-like cells

Cell-based therapies are used to treat bone defects. We recently described that human multipotent adipose-derived stem (hMADS) cells, which exhibit a normal karyotype, self renewal, and the maintenance of their differentiation properties, are able to differentiate into different lineages. Herein, we show that hMADS cells can differentiate into osteocyte-like cells. In the presence of a low amount of serum and EGF, hMADS cells express specific molecular markers, among which alkaline phosphatase, CBFA-1, osteocalcin, DMP1, PHEX, and podoplanin and develop functional gap-junctions. When loaded on a hardening injectable bone substitute (HIBS) biomaterial and injected subcutaneously into nude mice, hMADS cells develop mineralized woven bone 4 weeks after implantation. Thus hMADS cells represent a valuable tool for pharmacological and biological studies of osteoblast differentiation in vitro and bone development in vivo.

Isolated arthroscopic biceps tenotomy or tenodesis improves symptoms in patients with massive irreparable rotator cuff tears

BACKGROUND

Lesions of the long head of the biceps tendon are often associated with massive rotator cuff tears and may be responsible for shoulder pain and dysfunction. The purpose of this study was to evaluate the clinical and radiographic outcomes of isolated arthroscopic biceps tenotomy or tenodesis as treatment for persistent shoulder pain and dysfunction due to an irreparable rotator cuff tear associated with a biceps lesion.

METHODS

We conducted a retrospective study of sixty-eight consecutive patients (mean age [and standard deviation], 68 +/- 6 years) in whom a total of seventy-two irreparable rotator cuff tears had been treated arthroscopically with biceps tenotomy or tenodesis. A simple tenotomy was performed in thirty-nine cases, and a tenodesis was performed in thirty-three. No associated acromioplasty was performed. All patients were evaluated clinically and radiographically by an independent observer at a mean of thirty-five months postoperatively.

RESULTS

Fifty-three patients (78%) were satisfied with the result. The mean Constant score improved from 46.3 +/- 11.9 points preoperatively to 66.5 +/- 16.3 points postoperatively (p < 0.001). A healthy-appearing teres minor on preoperative imaging was associated with significantly increased postoperative external rotation (40.4 degrees +/- 19.8 degrees compared with 18.1 degrees +/- 18.4 degrees ) and a significantly higher Constant score (p < 0.05 for both) compared with the values for the patients with an absent or atrophic teres minor preoperatively. Three patients with pseudoparalysis of the shoulder did not benefit from the procedure and did not regain active elevation above the horizontal level. In contrast, the fifteen patients with painful loss of active elevation recovered active elevation. The acromiohumeral distance decreased 1.1 +/- 1.9 mm on the average, and glenohumeral osteoarthritis developed in only one patient. The results did not differ between the tenotomy and tenodesis groups (mean Constant score, 61.2 +/- 18 points and 72.8 +/- 12 points, respectively). The "Popeye" sign was clinically apparent in twenty-four (62%) of the shoulders that had been treated with a tenotomy; of the sixteen patients who noticed it, none were bothered by it.

CONCLUSIONS

Both arthroscopic biceps tenotomy and arthroscopic biceps tenodesis can effectively treat severe pain or dysfunction caused by an irreparable rotator cuff tear associated with a biceps lesion. Shoulder function is significantly inferior if the teres minor is atrophic or absent. Pseudoparalysis of the shoulder and severe rotator cuff arthropathy are contraindications to this procedure.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions to Authors for a complete description of levels of evidence.

Prothèse totale de hanche bilatérale en une session opératoire

PURPOSE OF THE STUDY

We conducted a prospective study of patients undergoing simultaneous bilateral total hip arthroplasty (THA) in order to assess perioperative complications. A review of the literature revealed the pertinence of surgical management of patients with invalidating bilateral degenerative hip disease using a single-stage procedure.

MATERIAL AND METHODS

Ten patients, four females and six males, mean age 57.8 years (range 33-71 year) were included in the study. The ASA classification was 1 for nine patients and 2 for one. The procedure was performed in the lateral reclining position using a posterolateral approach. Mean operative time was 212 minutes (range 165-270min) and mean blood loss as assessed by serum hemoglobin level was 9 mmol/l preoperatively and 5.93 mmol/l postoperatively. Three patients required transfusion. Mean hospital stay was 11 days (range 7-13 d). Leg length discrepancy improved from an average 4 mm preoperatively to 0.5 mm postoperatively.

RESULTS

One patient developed a sacral pressure sore which resolved in 21 days. One patient developed a wound infection (Pseudomonas aeruginosa) which resolved with local treatment. No other complication (death, pulmonary embolism, dislocation, deep infection, stiffness, heterotopic ossification) was observed 17.6 at 15 months of follow-up. There were no revision procedures. The Postel-Merle-d'Aubigné score improved from 9.6 preoperatively to 15 at mean follow-up (range 10-24 months).

DISCUSSION

Bilateral implantation of THAs in a single-stage procedure is indicated for chronic invalidating bilateral degenerative disease. About 0.5% to 3% of hip replacement procedures concern simultaneous bilateral implantations. The complication rate is no higher than after sequential surgery or even after single THA procedures, including the risk of pulmonary embolism. The cost of the procedure and the mean hospital stay are reduced compared with two operations. Rehabilitation is facilitated. The operative time is however longer and the risk of bleeding is increased but can be compensated for preoperatively and minimized intra- and postoperatively. This attractive strategy is not currently sufficiently reimbursed by the current conditions of the French health care insurance system.

[Percutaneous surgical treatment of two epiphyseal plate fractures of the proximal humerus]

We report two cases of Salter 2 displaced epiphyseal detachment of the proximal humerus treated successfully by percutaneous reduction and centromedular nailing. This surgical treatment was required because of the irreducibility of the lesion in one patient and instability in the other. This percutaneous technique can be recommended after failure of orthopedic treatment and is an attractive alternative to open surgery.

Ectopic bone formation using an injectable biphasic calcium phosphate/Si-HPMC hydrogel composite loaded with undifferentiated bone marrow stromal cells

We have used a new synthetic injectable composite constituted of hydroxyapatite/tricalcium phosphate (HA/TCP) particles in suspension in a self-hardening Si-hydroxypropylmethylcellulose (HPMC) hydrogel. The aim of this study was to evaluate in vivo the biocompatibility and the new bone formation efficacy of this scaffold loaded with undifferentiated bone marrow stromal cells (BMSCs). This biomaterial was mixed extemporaneously with BMSCs prepared from C57BL/6 mice, injected in subcutaneous and intramuscular sites and retrieved 4 and 8 weeks after implantation. Dissection of the implants revealed a hard consistency and the absence of a fibrous capsule reflecting a good integration into the host tissues. Histological analysis showed mineralized woven bone in the granule inter-space with numerous active osteoclasts attached to the particles as assessed by the presence of multinucleated cells positively stained for TRAP activity and for the a3 subunit of the V-ATPase. Small vessels were homogenously distributed in the whole implants. Similar results were obtained in SC and IM sites and no bone formation was observed in the control groups when cell-free and particle-free transplants were injected. These results indicate that this injectable biphasic calcium phosphate-hydrogel composite mixed with undifferentiated BMSCs is a new promising osteoinductive bone substitute. It also provides with an original in vivo model of osteoclast differentiation and function.

Proximal humerus fracture sequelae: impact of a new radiographic classification on arthroplasty

Our goal was to analyze the results of unconstrained shoulder replacement in a large series of sequelae of proximal humeral fractures in order to validate a previously described surgical classification. In a multicenter study, we retrospectively evaluated 203 patients with sequelae of proximal humeral fractures who were treated with a nonconstrained modular and adaptable prosthesis. The mean followup was 42 months (range, 24-96 months). We identified 137 impacted fractures with humeral head collapse or necrosis (Type 1 sequelae), 25 unreducible dislocations or fracture-dislocations (Type 2), 22 nonunions of the surgical neck (Type 3), and 19 severe tuberosity malunions (Type 4). Results of nonconstrained shoulder arthroplasty for the treatment of Type 1 and Type 2 sequelae were predictably good because no greater tuberosity osteotomy was performed. The distorted anatomy was accepted, and both the prosthesis and technique were modified accordingly. Total shoulder arthroplasty yielded better results than hemiarthroplasty. Patients with Type 3 or Type 4 sequelae had poor functional results with nonconstrained arthroplasty because greater tuberosity osteotomy was needed. This study validates our fracture sequelae classification. We no longer use unconstrained prostheses in Type 3 and Type 4 fracture sequelae and propose peg bone grafting or low-profile fracture prosthesis for patients with Type 3 sequelae and reverse arthroplasty for those with Type 4 sequelae.

LEVEL OF EVIDENCE

Prognostic study, level IV (case series). See Guidelines for Authors for a complete description of levels of evidence.

Anatomical consequences of “open-book” pelvic ring disruption. A cadaver experimental study

"Open-book" pelvic fractures associate a diastasis and/or a fracture of the pubic rami with a posterior pelvic disruption of the sacro-iliac joint. These uni or bilateral lesions are potentially lethal mainly due to associated injuries and massive pelvic hemorrhage. The most frequently injured arteries are parietal branch of the commune, internal or external arteries because of their proximity to the bone, the sacro-iliac joint and the inferior ligaments of the pelvis. The pelvic bone dislocation and the increase of pelvic volume facilitate blood effusion. The aim of this study was to determine, on a cadaver fracture model, the direct anatomical consequences of "open-book" pelvic fracture on the ilio-lumbar pedicle and the pelvic cavity volume.

MATERIALS AND METHODS

Bilateral open-book pelvic ring injuries were created in ten non-embalmed cadaver specimens by directly disrupting the pubic symphysis, the right and the left sacro-iliac joints. Pelvic volume was determined after total pelvic exenteration. Consequences of this fracture on vascular parietal network, nervous pelvic trunk and pelvic cavity volume were studied.

RESULTS

The mean volume of the pelvic cavity after complete visceral exenteration was 872.5 cm(3) (extremes 580-756 cm(3)). The average increase of pelvic volume was 20.8% after 5 cm of pubic diastasis. In all cases, because of a transversal disposition of the ilio-lumbar pedicle with regard to the sacro-iliac joint, reproduction of the open-book fracture caused a venous dilaceration of the ilio-lumbar vein in 12 cases after 5 cm of pubic diastasis (12/20=60%). No arterial dilaceration was observed on the ilio-lumbar artery, but this artery was put in tension.

CONCLUSION

Open-book fractures create an increase of pelvic volume that facilitates blood diffusion from parietal pelvic vascular network. Ilio-lumbar pedicle seems to be very vulnerable in this type of fracture because of its relations to the sacro-iliac joint and its transversal disposition with regard to this joint.

A silanized hydroxypropyl methylcellulose hydrogel for the three-dimensional culture of chondrocytes

Articular cartilage has limited intrinsic repair capacity. In order to promote cartilage repair, the amplification and transfer of autologous chondrocytes using three-dimensional scaffolds have been proposed. We have developed an injectable and self-setting hydrogel consisting of hydroxypropyl methylcellulose grafted with silanol groups (Si-HPMC). The aim of the present work is to assess both the in vitro cytocompatibility of this hydrogel and its ability to maintain a chondrocyte-specific phenotype. Primary chondrocytes isolated from rabbit articular cartilage (RAC) and two human chondrocytic cell lines (SW1353 and C28/I2) were cultured into the hydrogel. Methyl tetrazolium salt (MTS) assay and cell counting indicated that Si-HPMC hydrogel did not affect respectively chondrocyte viability and proliferation. Fluorescent microscopic observations of RAC and C28/I2 chondrocytes double-labeled with cell tracker green and ethidium homodimer-1 revealed that chondrocytes proliferated within Si-HPMC. Phenotypic analysis (RT-PCR and Alcian blue staining) indicates that chondrocytes, when three-dimensionnally cultured within Si-HPMC, expressed transcripts encoding type II collagen and aggrecan and produced sulfated glycosaminoglycans. These results show that Si-HPMC allows the growth of differentiated chondrocytes. Si-HPMC therefore appears as a potential scaffold for three-dimensional amplification and transfer of chondrocytes in cartilage tissue engineering.

Three-dimensional culture and differentiation of human osteogenic cells in an injectable hydroxypropylmethylcellulose hydrogel

The present work evaluates a newly developed silated hydroxypropylmethylcellulose (Si-HPMC)-based hydrogel as a scaffold for 3D culture of osteogenic cells. The pH variation at room temperature catalyzes the reticulation and self-hardening of the viscous polymer solution into a gelatine state. We designed reticulation time, final consistency and pH in order to obtain an easy handling matrice, suitable for in vitro culture and in vivo injection. Three human osteogenic cell lines and normal human osteogenic (HOST) cells were cultured in 3D inside this Si-HPMC hydrogel. We show here that osteosarcoma cells proliferate as clonogenic spheroids and that HOST colonies survive for at least 3 weeks. Mineralization assay and gene expression analysis of osteoblastic markers and cytokines, indicate that all the cells cultured in 3D into this hydrogel, exhibited a more mature differentiation status than cells cultured in monolayer on plastic. This study demonstrates that this Si-HPMC hydrogel is well suited to support osteoblastic survival, proliferation and differentiation when used as a new scaffold for 3D culture and represents also a potential basis for an innovative bone repair material.

The management of infection in arthroplasty of the shoulder

The management and outcome of treatment in 42 patients (49 shoulders) with an infected shoulder prosthesis was reviewed in a retrospective multicentre study of 2343 prostheses. The factors which were analysed included the primary diagnosis, the delay between the diagnosis of infection and treatment and the type of treatment. Treatment was considered to be successful in 30 patients (71%). Previous surgery and radiotherapy were identified as risk factors for the development of infection. All patients with an infected prosthesis had pain and limitation of movement and 88% showed radiological loosening. In 50% of the shoulders, the antibiotics chosen and the length of treatment were considered not to be optimal. The mean follow-up was 34 months. Antibiotics or debridement alone were ineffective. In acute infection, immediate revision with excision of all infected tissue and exchange of the prosthesis with appropriate antibiotic therapy gave the best results. Multidisciplinary collaboration is recommended.

The management of infection in arthroplasty of the shoulder

The management and outcome of treatment in 42 patients (49 shoulders) with an infected shoulder prosthesis was reviewed in a retrospective multicentre study of 2343 prostheses. The factors which were analysed included the primary diagnosis, the delay between the diagnosis of infection and treatment and the type of treatment. Treatment was considered to be successful in 30 patients (71%). Previous surgery and radiotherapy were identified as risk factors for the development of infection. All patients with an infected prosthesis had pain and limitation of movement and 88% showed radiological loosening. In 50% of the shoulders, the antibiotics chosen and the length of treatment were considered not to be optimal. The mean follow-up was 34 months. Antibiotics or debridement alone were ineffective. In acute infection, immediate revision with excision of all infected tissue and exchange of the prosthesis with appropriate antibiotic therapy gave the best results. Multidisciplinary collaboration is recommended.

[Entrapment of the long head of the biceps: the "hourglass biceps". Another cause of pain and locking of the shoulder]

PURPOSE OF THE STUDY

We describe a mechanical condition affecting the long head of the biceps tendon (LHBT) causing potentially unrecognized entrapment within the joint and subsequent pain and locking. This is caused by a hypertrophic intra-articular portion of the tendon that is unable to slide into the bicipital groove during elevation of the arm.

MATERIALS AND METHODS

Twenty one patients were identified, during open (14 cases) or arthroscopic (7 cases) surgery, with a so called "hourglass biceps" i.e., hypertrophic intraarticular portion of the LHBT and incarceration of the tendon during elevation. All cases occurred in conjunction with a rotator cuff rupture except one who had a partial deep tear. All patients were treated by excision of the biceps, after tenodesis or bipolar tenotomy, and appropriate treatment of the concomitant lesions.

RESULTS

All patients presented with anterior shoulder pain and loss of passive elevation averaging 10-20 degrees. A dynamic intraoperative test involving forward elevation with the elbow extended demonstrated entrapment of the tendon within the joint in each case. This test creates a characteristic "buckling" of the tendon and "squeezing" of the tendon between the humeral head and the glenoid ("hourglass test"). Excision of the tendon allowed immediate restoration of complete elevation. Mean Constant score increased from 38 points to 76 points postoperatively.

DISCUSSION

The "hourglass biceps" is caused by a hypertrophic intraarticular portion of the tendon that is unable to slide into the bicipital groove during elevation of the arm. Loss of 10-20 degrees of passive elevation, bicipital groove tenderness, and radiographic findings of a hypertrophied tendon can aid in diagnosis. The "hourglass biceps" should not be misdiagnosed for a frozen shoulder. Definitive diagnosis is made at surgery with the "hourglass test": incarceration and squeezing of the tendon within the joint during forward elevation of the arm with the elbow extended. Simple tenotomy cannot resolve this mechanical block. Either tenotomy with excision of the intraarticular portion of the LHBT or tenodesis must be performed. The "Hourglass" biceps is an addition to the familiar pathologies of the long head of the biceps tendon (tenosynovitis, prerupture, rupture, instability), and should be considered in any case of chronic anterior shoulder pain associated with a loss of shoulder elevation.

Shoulder arthroplasty for the treatment of the sequelae of fractures of the proximal humerus

The purpose of this multicenter study was to analyze the results of shoulder arthroplasty for the treatment of the sequelae of proximal humerus fractures and establish an updated classification system and treatment guidelines for these complex situations. Seventy-one sequelae of proximal humerus fractures were treated with shoulder replacement with the use of the same nonconstrained, modular, and adaptable prosthesis: the Aequalis prosthesis (Tornier Inc, St Ismier, France). The average time between initial fracture and shoulder arthroplasty was 5 years and 5 months. On the basis of anatomic classification schemes, sequelae were divided into 4 types: type 1, humeral head collapse or necrosis with minimal tuberosity malunion (40 cases); type 2, locked dislocations or fracture-dislocations (9 cases); type 3, nonunions of the surgical neck (6 cases); and type 4, severe malunions of the tuberosities (16 cases). The mean postoperative follow-up was 19 months (range, 12 to 48 months). Overall, the postoperative Constant score was excellent in 11 cases (16%), good in 19 cases (26%), fair in 18 cases (25%), and poor in 23 cases (33%). There were 18 complications (27%). Fifty-nine of 70 patients (81%) stated that they were satisfied with the result. The most significant factor affecting functional outcome was greater tuberosity osteotomy (P <.005). Regarding both surgical treatment and postoperative prognosis, we identify 2 categories of proximal humerus fracture sequelae: category 1, intracapsular/impacted fractures sequelae (associated with both cephalic collapse or necrosis [type 1] and chronic dislocation or fracture-dislocation [type 2]), in which an articulating joint can be reconstructed without a greater tuberosity osteotomy; and category 2, extracapsular/disimpacted fractures sequelae (associated with both surgical neck nonunions [type 3] and severe tuberosity malunions [type 4]) where the proximal humerus cannot be reconstructed without a greater tuberosity osteotomy. All of the excellent and good postoperative Constant scores were obtained in type 1 and 2, in which osteotomy of the greater tuberosity was not required. All patients in type 3 and 4, who underwent a greater tuberosity osteotomy, had either fair or poor results and did not regain active elevation above 90 degrees. We conclude that a greater tuberosity osteotomy is the most likely reason for poor and unpredictable results after shoulder replacement arthroplasty for the treatment of the complex sequelae of proximal humerus fractures. Shoulder arthroplasty for the treatment of the sequelae of fractures of the proximal humerus should be performed without an osteotomy of the greater tuberosity when possible. If prosthetic replacement is possible without an osteotomy, surgeons should accept the distorted anatomy of the proximal humerus and adapt the prosthesis and their technique to the modified anatomy. A modular and adaptable prosthesis with both adjustable offsets and inclination may allow surgeons to adapt to a large number of malunions and may help to avoid the troublesome greater tuberosity osteotomy in a higher proportion of cases.

The gene encoding the mouse homologue of the human osteoclast-specific 116-kDa V-ATPase subunit bears a deletion in osteosclerotic (oc/oc) mutants

Osteosclerosis (oc) is an autosomal recessive lethal mutation that impairs bone resorption by osteoclasts, and induces a general increase of bone density in affected mice. Genetic mapping of the oc mutation was used as a backbone in a positional cloning approach in the pericentromeric region of mouse chromosome 19. Perfect cosegregation of the osteopetrotic phenotype with polymorphic markers enabled the construction of a sequence-ready bacterial artificial chromosome (BAC) contig of this region. Genomic sequencing of a 200-kb area revealed the presence of the mouse homologue to the human gene encoding the osteoclast-specific 116-kDa subunit of the vacuolar proton pump. This gene was located recently on human 11q13, a genomic region conserved with proximal mouse chromosome 19. Sequencing of the 5' end of the gene in oc/oc mice showed a 1.6-kb deletion, including the translation start site, which impairs genuine transcription of this subunit. The inactivation of this osteoclast-specific vacuolar proton ATPase subunit could be responsible for the lack of this enzyme in the apical membranes of osteoclast cells in oc/oc mice, thereby preventing the resorption function of these cells, which leads to the osteopetrotic phenotype.

Lower limb trauma caused by power-driven cultivators: report of 23 cases

OBJECTIVE

To determine the mechanism and the severity of injuries caused by power-driven cultivators.

METHODS

This retrospective study analyzed the clinical records of 20 patients treated from 1984 to 1996 for a total of 23 lower limb injuries caused by power-driven cultivators (three patients had bilateral injuries) in the Nice University Hospital.

RESULTS

A total of 90% of the accidents occurred when the machine was put into reverse and the limb was caught by the rotary blades; the cause of the remaining accidents was unknown. Of the 23 patients, 10 patients (43.5%) suffered posterior dislocation of the knee due to forced hyperextension. Injuries were classed in two groups as a function of their prognosis: group I consisted of osteomuscular lesions without vascular or nerve involvement (11 lower limbs, 11 patients). The mortality rate in this group was 9%, the rate of major amputation was 18%, and the prognosis was favorable in 82% of the cases. Group II corresponded to lower limb injuries with neurovascular involvement (12 lower limb injuries in 10 patients: one patient belonged to both group I and group II). Acute lower limb ischemia was constant in group II; the mortality rate was 20% (two of 10 patients), and the rate of major amputation was 41.6% (five of 12 patients; three emergency amputations and two secondary amputations).

CONCLUSION

These agricultural machines can cause severe trauma, and the resulting wounds are contaminated by telluric germs in rural areas. Paradoxically, power-driven cultivators are not legally classified as "dangerous machines." Modification of existing legislation in this field would seem advisable.