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Academiejaar 2016-2017

PRONATOR SPARING PLATE OSTEOSYNTHESIS IN DISTAL RADIUS FRACTURES: EARLY FUNCTIONAL OUTCOME.

Kris MOENS

Promotor: Dr. Benis Szabolcs

Co-Promotor: Prof. Nadine Hollevoet

Masterproef voorgedragen in de master in de specialistische geneeskunde

Orthopedie

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Academiejaar 2016-2017

PRONATOR SPARING PLATE OSTEOSYNTHESIS IN DISTAL RADIUS FRACTURES: EARLY FUNCTIONAL OUTCOME.

Kris MOENS

Promotor: Dr. Benis Szabolcs

Co-Promotor: Prof. Nadine Hollevoet

Masterproef voorgedragen in de master in de specialistische geneeskunde

Orthopedie

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INHOUDSTAFEL:

INTRODUCTION

METHODS

RESULTS

DISCUSSION

REFERENCES

NEDERLANDSE SAMENVATTING

FIGURES

TABLES

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ABSTRACT:

INTRODUCTION: Thanks to modern anatomic stable angle plate and screw designs in

distal radius fractures, early mobilization is possible and pronation torque of the wrist is more

important in early recovery. Pronator sparing plate osteosynthesis of the distal radius is a

relatively new approach.

OBJECTIVES: A short overview of the technique is given with some tips and tricks. The

objective of the study is to investigate whether pronator sparing approach to distal radius

fractures gives better pronation force or grip force in the postoperative rehabilitation.

METHODS: Two randomly assigned groups of 30 patients with dorsally displaced unstable

wrist fractures, operated with or without pronator sparing plate osteosynthesis, were

retrospectively evaluated. Early postoperative grip force, pronator force and swelling were

compared to the contralateral side.

RESULTS: The pronator force on 3 weeks and 6 weeks was significantly higher in the

“pronator sparing” group, respectively 57% and 80% of the contralateral side compared with

43% and 67% in the “non sparing” group. Also swelling was significant less in the pronator

sparing group. There was no significant difference in grip force between the two groups.

CONCLUSION: Pronator sparing plate osteosynthesis in distal radius fractures seems to give

better pronation force and less swelling in early recovery after volar plate osteosynthesis. This

technique seems not to have beneficial results on grip force.

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INTRODUCTION

Volar fixed-angle plating for the repair of distal radius fractures has become the technique of

choice in recent years as it exhibits the potential for decreased functional disability and a

lower complication rate than alternatives such as external fixation, dorsal plating, or closed

reduction and casting/percutaneous pin fixation. The volar plate stabilizes the distal radius by

distributing the load in the subchondral bone, thereby minimizing the load across the fracture

site (1). In order to place a volar plate on the distal radius, the pronator quadratus (PQ) has to

be dealt with.

The PQ muscle is a quadrilateral muscle and is the deepest muscle in the anterior aspect of the

forearm (4). It consists of superficial and deep heads, which have different muscle fascicles

(8). A significant finding is that the most distal muscle fascicles reach the base of the ulnar

styloid process. This finding led us to conclude that the PQ muscle could provide the force to

shift the ulna proximally, and this function could prevent the head of the ulna from impacting

against the carpal bones. The PQ is innervated by the anterior interosseous nerve in a steady

pattern. The branches innervating the superficial head run on the radius from medial to lateral,

which suggests that surgeries for distal radial fractures should be conducted on the more

lateral side of the forearm (10).

Cadaver studies have confirmed the importance of the PQ muscle in the function of the

forearm and reported that the superficial head of the PQ muscle is the prime mover in forearm

pronation and the deep head is a dynamic stabilizer of the distal radioulnar joint (7). The

muscle is also important because it provides blood supply to the distal end of the radius,

which is believed to be of some importance to fracture healing (9).

An L-shaped incision of the PQ muscle along its radial and distal borders is the standard

technique for fracture reduction and internal fixation through the modified Henry approach.

The PQ muscle is prone to scarring, which may impede pronation and supination and may

also be a source of pain (4). Although PQ repair can often pose a major challenge, hand

surgeons commonly repair it for a number of reasons. It affects forearm stability and strength

and provides a soft-tissue interposition between the volar plate and flexor tendons,

conceivably decreasing tendon irritation problems (11). There is also a theoretical advantage

of preservation of the blood supply to the distal radio-ulnar joint (DRUJ), distal radius and its

periosteum by avoiding damage to the branches of the anterior interosseous artery passing

through the PQ (5,7).

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Recently, Dos Remedios et al have described a pronator-sparing technique during the volar

approach for plating of the distal radius in order to preserve the function and inherent

advantages of PQ (3). Unlike MIPO techniques, it is more a concept of minimal invasive

surgery during conventional approach (7).

There is still lack of reports on this PQ sparing technique and its clinical effects (4). The

objective of this retrospective study is to determine whether sparing the PQ muscle in placing

a volar plate for distal radius fracture has functional advantage in the early postoperative

period.

MATERIALS AND METHODS

Study population

Between 2009 and 2011, sixty patients underwent surgery for a distal

radius fracture with open reduction and internal fixation with a 2,4-

2,7mm AO palmar locking plate (Depuy-Synthes). All fractures were

classified according to the Frykman classification (fig. 1) and the

Orthopedic Trauma Association (AO/OTA) classification system (fig.

2). All cases were operated by the same

surgeon. In case of complex fracture patterns,

a CT scan with 3D reconstruction was made,

which is crucial in preoperative planning. Until

the day of surgery, an open cast was given to all patients. Indications

for surgery were dorsal angulation of more than twenty degrees,

radius shortening more than 5mm, dorsal comminution, articular

step-off more than 1-2mm or radial inclination less than fifteen

degrees. Volar displaced fractures were excluded.

The method of randomization was done on the basis upon arrival in the ER, in which we

switched both techniques between each patient.

The modified Henry approach has been imposed as the

standard anterior approach to the distal radius (14). A

longitudinal incision about 5cm over the tendon of flexor

carpi radialis (FCR) is made (fig. 3). After retracting the

FCR, the deeper sheath and fascia under FCR is released and

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the flexor pollicis longus (FPL) muscle is bluntly dissected and retracted towards the ulnar

side. Once the PQ is in sight, reduction of the fracture was done with percutaneous dorsal and

radial kirchner wires, which were removed after fixation with the

plate.

In group 1, the non-sparing group, the PQ is cut and sutured at the end

of the procedure, as shown in figure 4.

In group 2, the pronator-sparing group, instead of cutting the PQ, the

distal aponeurosis is incised and after undermining the muscle with an

elevator, plate insertion is done with the help of the fixed angle drill

guide. Locking of the plate is done with muscle splitting incisions through the muscle, after

ensuring adequate positioning of the plate on the radial shaft. Distal fixation is performed with

the fixed angle drill guide with locking screws. Two other proximal shaft screws are placed

through split incisions of the PQ (fig. 5). Postoperatively, all patients were immobilised in a

soft cast for two weeks.

Measurement

The assessment of the grip force was done with a baseline hydraulic dynamometer (BHD).

Pronation force was evaluated with the portable clinical assessment device as described by

Wong and Moskovitz (fig. 6) (13). Both pronation

and grip force were assessed as a percentage of the

normal contralateral side and every patient was tested

3 weeks and 6 weeks postoperatively. Swelling,

expressed as the circumference of the wrist in cm,

was also compared with the normal side.

Clinical evaluation

Patients were scheduled for follow-up at 3 and 6 weeks. Pain, forearm range of motion,

swelling, grip strength and pronation force were evaluated as well as radiographic follow up.

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Only swelling, grip force and pronation force were used in this study and compared with the

normal contralateral side.

Statistical analysis

Both groups were defined through surgical technique, means of age, sex distribution,

dominant side and fracture type. For statistical analysis, the SPSS software was used and a

Student’s T test was performed, comparing injured to the uninjured side concerning swelling,

grip strength and pronation force.

RESULTS

For this study, we made two groups of thirty people with a distal radius fracture with dorsal

displacement. The non-sparing group consisted of 11 men and 19 women with a mean age of

66 years. In 9 cases the fracture was extra-articular and in 21 cases intra-articular. The

pronator sparing group consisted of 5 men and 25 women with a mean age of 63 years. In 24

cases the fracture was intra-articular versus 6 extra-articular fractures (table I). In both groups,

the ratio dominant side/non dominant side was equal.

Pronation force and grip force are shown as a percentage of the force of the contralateral

normal wrist. Additional swelling of the operated wrist compared with the contralateral

normal wrist is also shown as a percentage. These results at three and six weeks postoperative

are shown in table II.

Non-sparing Pronator sparing

Number of patients 30 30

Mean age (years) 66 63

Male/female (n) 11/19 5/25

Dominant side/non dominant side 17/13 17/13

Intra-articular/extra-articular 21/9 24/6

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Frykman Classification

(n = number of patients)

Orthopedic Trauma Association

classification system

(n = number of patients)

Table I - Characteristics of patients

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Table II - Outcomes of pronator torque, grip force and swelling at 3 weeks and 6 weeks

follow-up

Pronation force:

Pronation force was found to be significant higher in the pronator sparing group (P<0,001)

both at 3 weeks and 6 weeks postoperatively (Table III).

Non-sparing group Pronator-sparing group

3 weeks postop 43% 57% P < 0.001

6 weeks postop 67% 80% P < 0.001

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Table III – Student’s T-test on pronation force at 3 and 6 weeks follow up

Grip force

Mean grip force was higher in de pronator sparing group, but was not significantly different

according to the Student’s T-test (Table IV).

Non-sparing group Pronator-sparing group

3 weeks postop 49% 51% Ns

6 weeks postop 65% 70% Ns

Table IV – Student’s T-test on grip force at 3 and 6 weeks follow up

Swelling:

Also swelling was shown to be significant lower in the pronator sparing group at 3 weeks and

6 weeks follow-up (table V).

Non-sparing group Pronator-sparing group

3 weeks postop 2,1cm 1,3cm P < 0.001

6 weeks postop 1,2cm 0,4cm P < 0.001

Table V – Student’s T-test on swelling at 3 and 6 weeks follow up

DISCUSSION

Distal radius fractures represent one of the most common fracture types observed in all age

groups (2). With the development of volar locking palmar plates, the volar approach to the

distal radius is being increasingly used for fracture management (4). Preservation of the PQ

has been suggested to have many benefits compared to release at its radial border (3). The

advantages cited in the literature are decreased stiffness, lower risk of postoperative tendon

rupture, additional stability of the distal radioulnar joint and preservation of the volar blood

supply to the distal radius and the capsule of distal radioulnar joint. By sparing the PQ, bone

union may be achieved more quickly and recovery time may be shorter (9).

There is little literature on pronation force in volar plating. Huh et al stated that with volar

plating, pronation strength was not significantly different between the operated and normal

sides at 1 year postoperatively, and decreases in pronation or supination strengths were not

found to affect clinical outcomes as assessed by DASH scores. They suggest that dissection of

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the PQ may have minimal clinical impact on forearm pronation function (6). Moreover the

benefit of repair of the PQ is being questioned in a study of Tosti and Ilyas, where PQ repair

after volar plating did not significantly improve postoperative range of motion, grip strength,

or DASH and VAS scores at 1 year (12). Research on the importance of PQ repair showed

that no statistical difference in ROM/grip strength or incidence of postoperative complications

was detected between the complete and incomplete PQ repair groups. Nevertheless, several

authors suggest to always make an effort to cover the plate during closure, since it serves as

protection against flexor tendon injury (1).

There is little literature that directly compares pronator repair and pronator sparing volar

plating. In a retrospective consecutive cohort study of Zenke et al, sixty-six patients

underwent surgery for distal radius fracture and they found no significant differences between

the minimally invasive plate osteosynthesis with PQ sparing and conventional plating based

on postoperative radiologic and clinical outcomes (15).

Recently, Fan et al published a comparative cohort study on a group of sixty-five patients

treated with volar plating for distal radius fracture, comparing the pronator sparing technique

with incising the PQ. At 1,2 and 6 weeks postoperatively, wrist pain, forearm range of

motion, grip strength and wrist function was significantly better. At 6 and 12 months

however, these differences were insignificant. Although there is no similar literature to

compare with, it is believed that this result is due to the fact that the PQ muscle was hardly

damaged, which allowed faster immediate functional recovery postoperatively. They

concluded that preservation of the PQ is a satisfactory method for the treatment of most of the

distal radiusfractures with volar locking palmar plates, as this technique can yield better early

wrist function and shorten the rehabilitation (4).

We believe this is the first study to compare the two groups of patients at 3 weeks and 6

weeks postoperative on terms of grip force, swelling and pronation force. PQ preservation

seems to give better early functional outcome on pronation force and swelling in volar plating.

Grip force is not significant better.

Force measurements were performed with the baseline hydraulic dynamometer. Wong and

Moskovitz concluded in their study that the BHD is a reliable and valid tool for measuring

forearm strength when outfitted with a doorknob-shaped handle. Moreover, the BHD showed

good intra- and interrater reliability and demonstrated moderate validity compared with

Cybex 6000 strength testing (13).

In this retrospective study there are some potential weaknesses. The follow-up period was

limited to six weeks and only sixty cases were considered. Prospective setups with a larger

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sample size and longer follow-up can provide more distinct evidence. Nevertheless we believe

that even in the absence of significant late postoperative clinical improvement, the

preservation of the PQ is a valid technique that can provide early clinical benefits.

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REFERENCES

1. Ahsan ZS, Yao J. The importance of pronator quadratus repair in the treatment of distal radius

fractures with volar plating. Hand (N Y). 2012; 7: 276-80.

2. Armangil M, Bezirgan U, Başarır K, Bilen G, Demirtaş M, Bilgin SS. The pronator quadratus

muscle after plating of distal radius fractures: is the muscle still working? Eur J Orthop Surg

Traumatol. 2014; 24: 335-9.

3. Dos Remedios C, Nebout J, Benlarbi H, Caremier E, Sam-Wing JF, Beya R. Pronator

quadratus preservation for distal radius fractures with locking palmar plate osteosynthesis.

Surgical technique. Chir Main. 2009; 28: 224-9.

4. Fan J, Chen K, Zhu H, Jiang B, Yuan F, Zhu X, Mei J, Yu G. Effect of fixing distal radius

fracture with volar locking palmar plates while preserving pronator quadratus. Chin Med J. 2014;

127: 2929-33.

5. Heidari N, Clement H, Kosuge D, Grechenig W, Tesch NP, Weinberg AM. Is sparing the

pronator quadratus muscle possible in volar plating of the distal radius? J Hand Surg Eur Vol.

2012; 37: 402-6.

6. Huh JK, Lim JY, Song CH, Baek GH, Lee YH, Gong HS. Isokinetic evaluation of pronation

after volar plating of a distal radius fracture. Injury. 2012; 43: 200-4.

7. Lo HY, Cheng HY. Clinical study of the pronator quadratus muscle: anatomical features and

feasibility of pronator-sparing surgery. BMC Musculoskelet Disord. 2014; 15:136.

8. McConkey MO, Schwab TD, Travlos A, Oxland TR, Goetz T. Quantification of pronator

quadratus contribution to isometric pronation torque of the forearm. J Hand Surg Am. 2009; 34:

1612-7.

9. Rey PB, Rochet S, Loisel F, Obert L. Technical note: How to spare the pronator quadratus

during MIPO of distal radius fractures by using a mini-volar plate. Chir Main. 2014; 33: 95-9.

10. Sakamoto K, Nasu H, Nimura A, Hamada J, Akita K. An anatomic study of the structure and

innervation of the pronator quadratus muscle. Anat Sci Int. 2014; Apr 12.

11. Swigart CR, Badon MA, Bruegel VL, Dodds SD. Assessment of pronator quadratus repair

integrity following volar plate fixation for distal radius fractures: a prospective clinical cohort

study. J Hand Surg Am. 2012; 37:1868-73.

12. Tosti R, Ilyas AM. Prospective evaluation of pronator quadratus repair following volar plate

fixation of distal radius fractures. J Hand Surg Am. 2013; 38: 1678-84.

13. Wong CK, Moskovitz N. New assessment of forearm strength: reliability and validity. Am J

Occup Ther. 2010; 64: 809-13.

14. Zemirline A, Naito K, Lebailly F, Facca S, Liverneaux P. Distal radius fixation through a mini-

invasive approach of 15 mm. Part 1: feasibility study. Eur J Orthop Surg Traumatol. 2014; 24:

1031-7.

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15. Zenke Y, Sakai A, Oshige T, Moritani S, Fuse Y, Maehara T, Nakamura T. Clinical results of

volar locking plate for distal radius fractures: conventional versus minimally invasive plate

osteosynthesis. J Orthop Trauma. 2011; 25: 425-31.

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NEDERLANDSE SAMENVATTING

Dankzij moderne anatomische hoekstabiele plaat en schroef designs voor de behandeling van

distale radius fracturen is vroegtijdige mobilisatie mogelijk. Pronator sparende plaat

osteosynthese van de distale radius is een relatief nieuwe toegangsweg, waarbij de pronator

quadratus niet doorgenomen, maar gespaard wordt tijdens de ingreep.

In dit artikel wordt een overzicht van de chirurgische techniek beschreven met toevoeging van

enkele tips en tricks. Het objectief van deze studie is te onderzoeken of een pronator sparende

approach van distale radius fracturen een betere pronatie kracht en/of grijpkracht geeft tijdens

de postoperatieve revalidatie. Tevens wordt nagegaan wat de invloed van deze operatieve

techniek op de zwelling is postoperatief.

Twee gerandomiseerde groepen van elk een 30-tal patiënten met dorsaal verplaatste

onstabiele polsfracturen welke ofwel volgens een klassieke toegangsweg waarbij de pronator

quadratus wordt doorgesneden en gereïnsereerd, ofwel volgens een pronator sparende

toegangsweg werden behandeld, werden retrospectief geëvalueerd. De postoperatieve

grijpkracht, pronatiekracht en zwelling werden vergeleken met de contralaterale zijde.

De pronatiekracht na drie en zes weken postoperatief was significant hoger in de pronator

sparende groep, respectievelijk 57% en 80% van de contralaterale zijde vergeleken met 43%

en 67% in de niet-pronator sparende groep. Daarnaast was ook de zwelling significant minder

in de pronator sparende groep. Wat het verschil in grijpkracht betreft tussen beide groepen

werd geen significant verschil aangetoond.

We kunnen concluderen dat pronator sparende plaat osteosynthese bij distale radius fracturen

een betere pronatiekracht en minder zwelling kunnen geven in het vroegtijdige stadium van de

revalidatie na volaire plaat osteosynthese voor dorsaal verplaatste onstabiele polsfracturen.

Deze techniek lijkt geen significant voordeel te hebben wat betreft grijpkracht.

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Fig. 1 - The Frykman classification

Fig. 2 - the Orthopedic Trauma Association (AO/OTA) classification

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Fig. 3 - A longitudinal incision about 5cm over the tendon of flexor carpi radialis (FCR)

Fig. 4 - Repair of the PQ muscle in the non-sparing technique (2)

Fig. 5 - Pronator sparing technique

Fig. 6 - Baseline hydraulic dynamometer (BHD) (13)

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Table I - Characteristics of patients

Non-sparing Pronator sparing

Number of patients 30 30

Mean age (years) 66 63

Male/female (n) 11/19 5/25

Dominant side/non dominant side 17/13 17/13

Intra-articular/extra-articular 21/9 24/6

Frykman Classification

Orthopedic Trauma Association

classification system

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Table II - Outcomes of pronator torque, grip force and swelling at 3 weeks and 6 weeks follow-up

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Table III – Student’s T-test on pronation force at 3 and 6 weeks follow up

Non-sparing group Pronator-sparing group

3 weeks postop 43% 57% P < 0.001

6 weeks postop 67% 80% P < 0.001

Table IV – Student’s T-test on grip force at 3 and 6 weeks follow up

Non-sparing group Pronator-sparing group

3 weeks postop 49% 51% Ns

6 weeks postop 65% 70% Ns

Table V – Student’s T-test on swelling at 3 and 6 weeks follow up

Non-sparing group Pronator-sparing group

3 weeks postop 2,1cm 1,3cm P < 0.001

6 weeks postop 1,2cm 0,4cm P < 0.001