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ORIGINAL ARTICLE

Design And Clinical Application Of Proximal Humerus Memory Connector

Sun jianwei* ,Zhang Chuncai, Xu Shuogui

* Department of orthopaedics, Changhai Hospital, Shanghai, China200433

Address for Correspondence:

Sun jianwei
Department of orthopaedics, 
Changhai Hospital, Shanghai, China
200433

Abstract:

To research a new method to treat the fracture and nonunion of the region from anatomical neck to the diaphysis part of the proximal humerus. According to the mechanical character of bio memory material Nitional and the physiological character of proximal humerus, a new device called proximal humerus memory connector was designed. 22 cases of comminuted fracture, malunion and nonunion of proximal humerus were treated by this device. The healing style was characterized by plate bone substitution, no disordering callus was observed. The function of the shoulder was scored average 88.5 according to the criteria of Michael Reese. PHMC is an efficacious method to treat every type fractures and nonunion of the region from anatomical neck to the diaphysis part of humerus, and a new way is explored to reduce the rate of prostheses displacement of this part.
Keywords: Humeral fractures; Shoulder fractures; Proximal humerus memory connector

J.Orthopaedics 2007;4(2)e38

 
Introduction:

The 4-5% of all the fracture is the fracture of proximal humerus [1-2].For dislocated comminuted fracture of proximal humerus , the steel plate and bolt system made of the austenitic material sometimes is difficult to find point of resistance force in order to maintain restitution and fixation effectively,and furthermore the ununited fracture and ischemic necrosis of caput humeralis are common[1,3]. Conservative treatment often leads to pain and different degrees of disability because of metachoresis and compareed long-term external fixation[4,5] So the reports of the prosthetic replacement are seen frequently[6]. Owing to this, the author invents the proximal humerus memory connector(PHMC),according to the characteristic of the nitinol alloy [7]and the anatomic figure of proximal humerus .from August 2000 to September 2003, total 22 cases of fracture malunion and ununited fracture of proximal humerus had been treated by PHMC. Now we reports as follow.

Design,principle and application

The Structure Design

According to the anatomic and biomechanical features of proximal humerus, choosing 2 to 2.5mm thickness nickel 50at%~53at% nitinol plate, the PHMC is designed to consist of head part, axial compression part and body part(see fig.1). The head part consists of directing fixing branch for caput

humeralis and humerus semiring holding branch for anatomical neck. The holding plate and holding wing compose body part.It is treated to have one way memory effect and recovery temperature is 33±2. According to the fracture type, The PHMC is designs to typeand type .Each type consists of  different sizes.  

The Principle

The head body and compression part are deformated in low temperature to fit the figure of operation region on proximal humerus.The metallography of PHMC is changed by body temperature,which leads to mechanics proceeding. (1) Directing fixing branch and  semiring holding branch stabilize disclosed caput humeralis. (2) The standard body part will hold the “non-standard” tubular bone on with multipoint fixation. The hooks of axial compression parts will be inserted into the holes on two side of the fracture. (3)The directing fixing branch and compression branch which are restricted by the bone hole when reverting to their original shapes exert continuously memory compressure at the fracture line. Because of above mentioned 3 reasons, PHMC and two ends will compose 3D mnemonic fixation.

The Method of Application

According to the type,of fracture, the type and size of PHMC are decided before operation. General anaesthesia or block anaesthesia of brachiplex is applyed. Semirecumbent position is taken . Anteriomedial approach of shoulder is chosed . The incision can be extended to acromial process if necessary. The incision to ilium is prepared.

(1)The fracture of greater tubercle lesser tubercle and surgical neck or anatomical neck of  humerus. The fracture site is explored ,a bone channel which diameter is 0.4-0.6 cm is drilled on the site 0.5-1.0 cm below the tip of greater tuberosity of humerus, casting shadow to the center of caput humeralis and not  piercing through articular facet. And then the directing fixing branch of the PHMC is inserted into the channel. The points for semiring holding branch inserting are determined, the pores are drilled ,and then the branches are inserted into the pores. The head part of PHMC is rewarmed. And then, the body part of  PHMC is inserted, the holding wings fix the distal end of fracture, and PHMC is rewarmed. At last, the points for axial compression part which is plastic formed and expanded are determined , the pores are drilled ,and then the part is inserted into the pores. The part is rewarmed. So the whole fixation is completed.

(2) The nonunion of surgery neck of  humerus. The scar and free bone sequestrum are removed to expose the cancellated bone of the proximal end of the nonunion. The medullary cavity of distal end is drilled through. Then the PHMC is applyed. At last, the holding wing of PHMC is cooled and spread out of bone. The iliac grafting bone composed of cancellated bone and cortical bone is put into the space between bone and PHMC, which spanned the fracture site like splints. The cancellated bone is towards the nonunion while the cortical bone is towards the PHMC. Finally, PHMC is rewarmed and fixes the nonunion.The spatium between PHMC and bone is filled with scum of spongy bone.

(3) The serious comminuted fracture or compressed defection of greater tubercle lesser tubercle and surgical neck of humerus. The large surface of iliac bone graft is taken to contact the cancellated bone of cancellated bone ,while the small end of the graft is inserted into the medullary cavity of distal diaphysis.

(4) The serious comminuted fracture or compressed defection of greater tubercle lesser tubercle and surgical neck and comminuted fracture of proximal 1/3 diaphysis of humerus. At first comminuted fracture of diaphysis is reduced and fixed by arched toothed nails from far distally to proximum; The subsequent processes are applyed according to above (3) (1).

(5) The articular capsule and rotator cuff can be tied to the semiring holding branch for anatomical neck of humerus. 

Postoperative Management

(1) Drainage. A drainage will be retained for 24~48h in cases of fractures and nonunion.

(2) stopping. Suspension with triangular bandage for one week generally.

(3) Functional exercise. About 2 days after operation, the patient should begin to contract the muscle group of upper arm actively and gradually.And about 2 weeks after operation, the patient should begin to flex or extend the shoulder actively and gradually.

(4) Removement of PHMC. 10-18 months after operation, PHMC can be removed by choosing the primary incision, refrigerating PHMC, then prying the hooks of compressing branch and semiring holding branch, and spreading the wings at last.

Figure 1.The delineation of PHMC and delineation of its plastic formation

Figure 2. Female,15 years old. a. The AP plate of shoulder joint 30 days after injury shows the fracture of proximal humerus of  Neer Ⅵ .b. The oboslete fracture of anatomical neck and dislocation of caput humeralis.There is 3.7cm's displacement between ends of fractured bone.

 

Figure 3 . male,13 years old. a. The AP plate of sholder shows malunion of fracture of surgical neck of humerus. enstrophe angle of caput humeralis is 100 ° b. The AP plate of sholder 6 months after operation fixed by PHMC Ⅱ,rectified by osteotomy shows  the anatomic synostosis between caput humeralis and anatomical neck.

Figure 4. male,37 years old. a. The AP plate of sholder shows fracture of surgical neck of humerus 11 months after ORIF by steel plate,100 °'s enstrophe angle of caput humeralis and nonunion of fracture. b. The AP plate of sholder 5 months after the operation fixed by PHMC shows anatomic synostosis.
Figure 5 . male,65 years old. a.The AP plate of sholder shows the fracture of greater tubercle lesser tubercle and surgical neck,the compressed defection of medial anatomical neck and the semiluxation of  caput humeralis. b.c.d applying the circle temporarily made by steel wire prevent bone pieces dispersing .e. The plate one and a half years after operation
<
Figure 6 .male,44 years old. a. The fracture of surgical neck associated with comminuted fracture of proximal 1/4 of diaphysis. b. Applying arched toothed nail to fix the bone pieces,finding foothold to apply bone graft and then whole fixing fracture by PHMCⅡ.c. The plate of shoulder 5 months after operation shows synostosis.

Results :

Clinical result: 

Common Information

Total 22 cases include comminuted fracture malunion and ununited fracture of proximal humerus were treated by PHMC.There are 13 cases of fracture ,involving greater tubercle lesser tubercle surgical neck and anatomic neck,4 cases of malunion and 5 cases of ununited fracture among them. There were 15 males and 7 females. The age ranged from 13 to 69 years (arerage 41.7 years); 

Result

All cases were followed up from 6 to 37 monthes, average 18.5 months. The fracture attained synostosis at an average time of 3.6 monthses ,and the ununited fracture was at 4.5 monthses. All the fracture sites were replaced by lamellar bone,and there were no disordered bony callus .External fixation was not needed after operation by PHMC.After trauma response (about 7-12 days after operation), the patient should begin to functional exercise actively and gradually. The average score of shoulder joint function is 88.5 according to the criteria of Michael Reese [9]  

Conclusion:

3D Biomechanic Characteristics of  PHMC[10-13]

(1) The  directing branch  of head part and the semiring holding branch outside the articular capsule and the axial compression part  provide the mnemonic compressive stress that does not disappear because of absorption of fracture line. It can provide dynamic stimulus for the ossification.

(2) The stabilization of multiple points providing by difference between internal diameter of PHMC and external diameter of bone belongs to the 3D stabilization of non- axis and non- side wall.

(3) The patient can do functional exercise actively and gradually after trauma response (7-12 d). so the PHMC not

only can stabilize  bone pieces, but also can accustom the straining of the muscle group on the place . 

The Indication of  PHMC

The various fracture and nonunion of the region from anatomical neck to the diaphysis part of the proximal humerus. 

The Characteristic and Management of Above Region

On one hand, comminuted fracture of  the region usually have different compressed  cancellous defect. On the other hand, cortical bone of the surgery neck is thin. So it is difficult to find fixing location if crashed. There is more hollow yellow marrow on surgical neck of the old, so it is difficult to get supporting locoation to reunion if crashed. These characteristics put forward the problems how to apply bone graft. The tips for bone graft are as follows.

(1) Building up the fulcrum of defection. The iliac bone block is chiseled from the site 4cm behinds anterior superior iliac spine, extending 2-3cm along iliac crest backwards, then descending 4cm down. So the bone graft is about 4cm long and 2-3cm wide. The crest of iliac bone graft is broadest position of iliac bone graft . The cancellated bone of it is exposed.The large surface of iliac bone graft is taken to contact the cancellated bone of cancellated bone. Another end of iliac bone graft is trimmed the same size of the medullary cavity and inserted into the cavity.

(2) Filling up the space surrounding the defection The space between PHMC and bone is filled with mixed scum of ilium and recombinated heterogeneic bone.

(3) Build up the exterior anatomic form of the defection. The bone stick spanned the defection like splints, clamped by bone holding wing.

Above 3 points fits the case of nonunion,too. Comprehensive treatment is applied to the special case showed by fig.5 and fig.6. 

The Characteristic of Fixation and Ossification of  PHMC

The 3D mnemonic dynamic mechanic environment of PHMC, the characteristic of bone graft and the anatomic figure of proximal humerus effect each other.which creats multipolar 3D force field. The difference of diameter between PHMC and bone and multipoint fixation promote the recovery blood supply. The mnemonic compression between fracture site promotes the ossification. All the fracture sites were replaced by lamellar bone,and there were no disordered bony callus. This kind of healing appears accompanying with the active and gradual functional exercise after trauma reaction.The unification of valid fixation, ossification, function recovery is attained on the whole [10,11].  

The Clinical Significance of  PHMC

For the fracture of the region from anatomical neck to the surgical neck of the proximal humerus,the prosthetic replacement is recommended more and more frequently. The reason is as follows. At first,It is difficult to fix this kinds of fracture by plate and/or tension band; On the orther hand, Kuner etc.[14]  report the rate of ischemic necrosis of caput humeralis is 44.6% for the fracture of proximal humerus fixed by plate, the rate is 33.3% for the fracture limited fixed by

screw tension band and polydimethylsiloxane(PDS). The result of prosthetic replacement caused by ischemic necrosis for the old is fair, but for the young, the problem caused by replacement also allows of no  optimism[15]. The result of study shows the PHMC can make the fracture attain anatomic reduction and bone healing, There is no report of ischemic necrosis so far. Certainly, we still needs the long-term observation on the big sample, but at least the case showed by fig.4 is worth us more exploration and thought. 

The Limitation of  PHMC

The PHMC is not suitable for compressed comminuted fracture of the region from anatomical neck to the caput humeralis. How to fix this kind of fracture effectively, reduce the prosthetic replacement and recover the function as soon as possible is still a topic that needs to continue to approach.

References :

  1. Browner, D. et al, Skeletal traumaEnglish copy1st , Science Publisher  (Bei  Jing, 2001). pp. 1570-1571.

  2. Qu, W., Wang, S. F., et al,. “Treatment of fracture of  proximal humerus by AO LPHP.”,J China Trauma, vol 19 (2003), pp,625-627.

  3. Kocialkowski, A., Wallace, W. A., “Closed percutaneous K-wire stabilization for displaced fractures of the surgical neck of the humerus”. Injury, vol 21,(1990), pp,209-212.

  4. Stableforth, P. G., “Four-part fractures of the neck of the humerus”. J Bone Joint Surg (Br), vol 66,1984, pp,104-108.

  5. Moda S K, Chadha N S, Sangwan S S, et al. “Open reduction and fixation of proximal humeral fractures and fracture-dislocations”. J Bone Joint Surg (Br), vol 72 (1990), pp, 1050-1052.

  6. Lin, H. S. ,Zha ,Z .G., Wang ,G .J ,et al, “Treatment for coplex fracture of proximal humerus by artificial caput humeralis”. J China Trauma, vol19,( 2003), pp,410-412.

  7. Otsuka, K, Wayman ,C.M. ,Shape memory materials. (Translated by Zhang ,C. C, Su ,J C, et al).1st.  Smmu Publisher (Shang Hai 2003). pp, 189-197.

  8. Arched toothed memory bone connectortype I,PRC. Patent ZL 01 3 44222.8

  9. Dai ,K.R.,e t al,  Surgeryof  shoulder  1st. People’s Health Publisher, (Bei Jing1992)  pp, 401-403.

  10. Zhang ,C. C., Xu ,S.G., Wang, J. L .,et al. “Design and clinical applications of swan-like memory-compressive connector for upper limb diaphysis”, Tans of smmuvol22(2001),pp,939-942.

  11. Zhang,C.C.,Xu,S.G., et al. “Design and clinical applications of swan-like memory-compressive connector for upper limb diaphysis”. Material Science Forum 2002, pp, 33-36.

  12. Xu,S.G.,Zhang,C.C.,Su,J.C.,et al. “The vitodynamic study of the treatment of ununited fracture  and fracture of humerus by swan-like memory-compressive connector.” Tans of smmuvol22(2001)pp,946-948.

  13. Xu,S.G.,Zhang,C.C.,Su,J.C.,et al. “The 3D finite element analysis of the treatment of ununited fracture  and fracture of humerus by swan-like memory-compressive connector.” Tans of smmuvol22(2001)pp,943-945

  14. Kuner ,EH, Siebler G. “Luxationsfrakturen des proximalen Humerus---Ergebnisse nach operativer Behandlung---Eine AO-Studie über 167 Fälle”.Unfallchirurg, vol.100, ( 1987), pp,64-71.

  15. Speck M, Regazzoni P. “Vier-Fragment-Frakturen des proximalen Humerus: Alternative Strategien der chirurgischen Behandlung”. Unfallchirurg, vol. 100, ( 1997), pp, 349-353. 

 

This is a peer reviewed paper 

Please cite as :Sun jianwei : Design And Clinical Application Of Proximal Humerus Memory Connector

J.Orthopaedics 2007;4(2)e38

URL: http://www.jortho.org/2007/4/2/e38

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