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Locking Compression Plates for Osteoporotic Nonunions of the Diaphyseal Humerus

Ring, David*; Kloen, Peter; Kadzielski, John*; Helfet, David; Jupiter, Jesse, B*

Section Editor(s): Strauss, Elton MD

Clinical Orthopaedics and Related Research: August 2004 - Volume 425 - Issue - p 50-54
doi: 10.1097/01.blo.0000131484.27501.4b
SECTION I: SYMPOSIUM: Geriatrics in Orthopaedics
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Poor bone quality increases the technical difficulty and complications of operative treatment of nonunions and delayed unions of the diaphyseal humerus in older patients. Plates with screws that lock to the plate (transforming each screw into a fixed blade) are intended to improve the fixation of poor quality bone. Twenty-four patients (20 women, four men) with an average age of 72 years (range, 52–86 years) were followed up for a minimum of 12 months after locking compression plate fixation of an osteopenic delayed union (nine patients) or nonunion (15 patients) of the diaphyseal humerus. Twelve patients had iliac crest cancellous bone grafts, two patients had local graft, and 13 patients had demineralized bone applied to the fracture site. All the fractures eventually healed; two healed after a second procedure for autogenous bone grafting in patients who initially received demineralized bone. Using a modification of the Constant and Murley shoulder score, the results were good or excellent in 22 patients, and fair in two patients. Locking compression plates provide stable fixation of poor quality bone in patients with delayed union or nonunion of the humerus. Successful union and restoration of function are achieved in most patients. We no longer consider osteoporosis a contraindication to operative fixation of an ununited fracture of the humeral diaphysis.

From the *Department of Orthopaedic Surgery, Massachusetts General Hospital, Boston, MA; †Department of Orthopaedic Surgery, Academic Medical Center, Amsterdam, The Netherlands; and the Hospital for Special Surgery, New York, NY.

Financial support from an unrestricted research grant from AO Foundation.

Correspondence to: David Ring, MD, ACC 525, 15 Parkman Street, Boston, MA 02114. Phone: 617-724-3953; Fax: 617-726-8214; E-mail: dring@partners.org.

Guest Editor

With improvements in preventative medicine, medical care, and lifestyle, patients are living longer and remaining healthy and active at older ages.8,23 As a result, fractures in individuals with osteoporosis are increasingly common. Many of these fractures and their sequelae will benefit from operative fixation, but operative fixation can be challenging when the bone is of poor quality. When reconstructive procedures are considered, there often has been a period of disuse—related for instance to a painful, unstable nonunion—that additionally diminishes bone quality.14 Prior operative procedures and loose implants also may compromise bone quality.18,22 Relative or absolute bone defects prevent compression of fracture surfaces, which increases the stress on implants.21

Several techniques have been suggested for improving internal fixation of osteoporotic bone including augmentation of screw fixation with bone cement,1,7,19,20,26,27,29 application of a strut of cortical bone (usually allogenic),3,5,6,12,22,28 exchange of loose 4.5-mm cortical screws with 6.5-mm cancellous screws,22 and application of an ancillary intramedullary plate to substitute for a deficient or osteoporotic opposite cortex.9,17 Although these techniques are useful, each has specific drawbacks that limit their appeal.

Initial success with fixed-angled implants such as the blade plate2,13,15,24 has led to the development of screws that are fixed rigidly to the plate at first by adding Schuhli nuts to standard plates16,25 and now with threaded holes incorporated directly into the plate in the so-called locking compression plate (Synthes, Paoli, PA). We reviewed our results using the locking compression plate for internal fixation of delayed unions and nonunions of the diaphyseal humerus in older individuals with osteoporosis to determine the rate of plate loosening and fracture nonunion.

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MATERIALS AND METHODS

Twenty-four patients with a delayed union or nonunion of the diaphyseal humerus and osteoporotic bone had open reduction and internal fixation with a 4.5-mm narrow locking compression plate. This represents the consecutive experience of three surgeons during an 18-month period. A delayed union was defined as the absence of radiographic progression of healing and an unstable fracture on clinical examination between 4 and 6 months after injury. The same criteria qualified as a nonunion greater than 6 months after the injury. Our Human Research Committee approved a protocol for retrospective evaluation and selective invitation to return for free examinations and radiographs.

There were 20 women and four men with an average age of 72 years (range 52–86 years). The right arm was fractured in 16 patients (all dominant) and the left arm was fractured in eight patients (none dominant). Nine patients had a delayed union and 15 patients had a nonunion. The fracture involved the proximal ⅓ of the diaphysis in 16 patients, the middle ⅓ in five patients, and the distal ⅓ in three patients. Eighteen patients did not respond to treatment with a functional brace, four patients did not respond to treatment with intramedullary rod fixation, and four did not respond to treatment with plate and screw fixation.

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Operative Technique

The Locking Compression Plate (Synthes) incorporates the option of threaded screw holes into a standard bone plate (Figs 1, 2). The previous standard dynamic compression unit plate hole has been replaced by a figure-of-eight screw hole with a threaded hole on one end and an oval dynamic compression unit on the other end. If osteoporosis sufficient to compromise screw engagement was not anticipated, the surgeon easily can switch to a screw fixed rigidly to the plate. All the functions of a standard dynamic compression plate are retained. The locking screws have threads on the head of the screw that engage the plate. They are slightly larger (5-mm diameter) and have very shallow threads (large core diameter) compared with standard 4.5-mm cortical screws (Fig 1).

Fig 1.

Fig 1.

Fig 2.

Fig 2.

The operative technique for Locking Compression Plates differs slightly from standard compression plating. For both techniques, we recommend that the operative exposure preserve periosteal and muscle attachments as much as possible. An anterolateral exposure was used in 21 patients11 and a modified posterior exposure was used in three patients.10

Locking screws require precise engagement of the screw threads with the plate threads. This is achieved by drilling the screw tract through a drill guide that threads into the screw hole in the plate.

Locking screws do not bring the plate to the bone. Plate-bone contact is not as important for a Locking Compression Plate as for standard compression plates. The diminished contact even may increase the blood supply to the bone and enhance the biologic aspects of healing.

Some plate-bone contact is useful to ensure fracture alignment and diminish the prominence of the implant. Plate-bone contact can be achieved by using a few standard screws to bring the plate to the bone (Fig 2). Alternatively, there is a device that drills into the bone and can be used to bring the plate to the bone.

A 4.5-mm narrow locking compression plate was used in each patient. The length of the plate averaged 10 holes (range, 6–14 holes). Twelve patients had iliac crest cancellous bone grafts, two patients had local graft, and 13 patients had demineralized bone applied to the fracture site.

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Postoperative Treatment

The surgically treated limb was supported in a simple sling after the operation. The patients discarded the sling as soon as comfort allowed, usually within a few weeks. Functional use of the limb for light tasks was allowed immediately after surgery. Pendulum exercises were initiated within a few days of surgery. Active assisted shoulder and elbow exercises were initiated between 4 and 6 weeks after surgery. Resistive exercises were initiated between 8 and 10 weeks after surgery.

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Complications and Subsequent Surgery

Two patients, both of whom received demineralized bone at the index surgery, had limited radiographic signs of healing 4 months after surgery and were reoperated on for a secondary iliac crest bone grafting (both patients had received demineralized bone). Additional complications included two transient radial nerve palsies, one iliac crest fracture, and one fracture above the plate treated with a second operation required for internal fixation.

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Evaluation

The patients were followed up for an average of 20 months (range, 12–36 months). The final results are reported after all secondary surgeries. The functional results were evaluated using a modification of the Constant and Murley shoulder score.4,22 Union was defined by progressive obscuring of the fracture line by new bone formation and the absence of loosening or breakage of the plate and screws 12 months or greater after surgery.

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RESULTS

All the fractures healed. There were no loose or broken implants. Forward flexion averaged 140° (range 90°– 170°) and external rotation averaged 50° (range 35°–70°). The limb was stable in all patients. Nine patients complained of continued pain, attributable to glenohumeral arthritis in two patients. All patients had a normal peripheral nerve examination. Using the Constant and Murley shoulder score, the results were good or excellent in 22 patients and fair in two patients.

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DISCUSSION

To our knowledge, there is only one previous study of the treatment of delayed and nonunion of the diaphyseal humerus in individuals with osteoporosis.21 This study documented successful treatment of osteoporotic nonunions of the diaphyseal humerus using various techniques to enhance fixation. Twenty-two patients with an average age of 72 years had plate fixation and autogenous cancellous bone grafting with one or more modifications of standard plate and screw techniques used to address osteopenia: long plates were used (average, 11 holes or 76% of the length of the bone); plates with a blade modification were used in 15 limbs; replacement of loose 4.5-mm cortical screws with 6.5-mm cancellous screws was done in 12 patients; Schuhli nuts were used in six patients. Two patients had an allograft strut applied, two patients had an intramedullary plate, and two patients had augmentation of screw fixation with cement. The fracture united in 20 patients (91%). Progressive loosening or breakage of the fixation was not observed, even in the two patients with a radiographic appearance suggesting incomplete union. Seventeen patients had satisfactory results according to a modification of the Constant and Murley shoulder score. All 22 patients had functional improvements, even the two patients with incomplete union. Although all of these techniques are useful for enhancing fixation of the osteoporotic bone, each has important drawbacks.

The drawbacks of cement enhancement of screw fixation include difficulty handling the cement and keeping it out of the fracture site. In addition, the cement cures through an exothermic reaction, the heat from which may kill adjacent cells and inhibit the biologic aspects of healing. Finally, the cement represents a large, intraosseous foreign body that may prove problematic if additional surgery is needed and will present a major problem if there is a deep infection.

The major drawback of the use of allograft struts to enhance fixation is the need for substantially greater soft tissue stripping in most cases to apply the strut. This stripping disrupts the blood supply to the fracture fragments and interferes with the biologic aspects of healing. In addition, allograft struts add little to the biology of healing and incorporate very slowly. Therefore, they represent a large foreign body that may increase susceptibility to deep infection.

The most useful technique for internal fixation of osteoporotic metaphyseal bone has been blade plate fixation.2,13,15,24 The broad blade is an inherent part of the plate that does not depend on thread-bone engagement for function. For a blade to fail completely, a substantial amount of underlying bone would have to fail. Blade plates have been used successfully to enhance the fixation of osteoporotic fractures of the proximal humerus.2,13,15,24

This concept was expanded to standard screws, with development of the Schuhli nut to convert standard screws to screws that lock rigidly to the plate, making each screw a fixed-angle blade.16,25 The Schuhli nut had spikes that engaged the bone to improve plate-bone friction. The nuts were placed underneath the plate so that the plate stood away from the bone. Some have likened this to an internal-external fixator.16,25 It was necessary to use small washers with the screws to ensure that the screw threads would engage the Schuhli nut, because standard screws had a threadless area adjacent to the screw head. Use of the Schuhli nut requires anticipation of poor quality bone and meticulous preoperative planning. A preliminary construct must be constructed and applied with the Schuli nuts held in place by plastic screws. When the construct is in place, standard screws are drilled and placed. The technique greatly enhances fixation of osteoporotic bone,21 but was tedious and demanding, and added several additional steps to the surgery.

With the locking compression plate, screws can lock directly into the plate. This is technically much easier to use, osteoporotic bone does not need to be anticipated, and the ability to apply compression is retained. We have found this plate to be very easy to use and our data show reliable fixation, a high union rate, and good restoration of function. The limitations of this investigation are those inherent to a retrospective case series, but probably are unavoidable because of the relative infrequency of the problem, the rapid evolution in techniques, and the lack of a suitable and acceptable control. Our findings would be supported by future reports from other surgeons. One concern in the use of these plates is direct pullout of the locked bolts because of their shallow threads. This has been observed with locking plates on the clavicle, tibia, and femur, but we have not observed this in the humerus.

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